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Disorder-specific Effects of CBT for Anxious and Depressed Youth: A Meta-analysis of Candidate Mediators of Change Brian C. Chu Tara L. Harrison Published online: 6 November 2007 Ó Springer Science+Business Media, LLC 2007 Abstract The commonalities between anxiety and depression have been discussed before, but few have delineated the potentially different mechanisms through which treatments work for these populations. The current study conducted a comprehensive review of child and adolescent randomized clinical trials that tested cognitive- behavioral therapy (CBT) for anxiety or depression. All studies were required to have assessed both treatment outcomes and at least one theory-specific process target, including behavioral, physiological, cognitive, and coping variables. Using a meta-analytic approach, CBT demon- strated positive treatment gains across anxiety, depression, and general functioning outcomes. CBT for anxiety also produced moderate to large effects across behavioral, physiological, cognitive, and coping processes, with behavioral targets demonstrating potentially the greatest change. CBT for depression produced small effects for cognitive processes but nonsignificant effects for behav- ioral and coping variables. Findings were generally consistent with CB theory but suggest potentially different mediators in the treatment of anxiety and depression. Results are discussed in terms of implications for mecha- nisms research, theories of change, and treatment development. Keywords Child Á Adolescent Á Anxiety Á Depression Á CBT Á Mechanisms of change Introduction The case for studying mediators of change in child and adolescent treatment research has been made before (Kazdin and Kendall 1998; Kazdin and Weisz 1998). Identifying the critical ingredients and the mechanisms through which treatments work is essential for maximizing treatment efficacy, improving therapeutic techniques, and improving methods for training therapists (Kazdin and Nock 2003; Weersing and Weisz 2002). Despite the importance of this research, there is a noted gap between our knowledge of treatment outcomes and the processes associated with those outcomes (Shirk 2005; Silverman 2006). The current review and meta-analysis will evaluate the specific effects that cognitive-behavioral therapy (CBT) produces in the treatment of anxious or depressed children and adolescents. Overlapping Features of Youth Anxiety and Depression Combined, anxiety disorders such as generalized anxiety disorder (GAD), separation anxiety disorder (SAD), social phobia (SOC), and other phobic disorders are estimated to represent the largest class of childhood emotional problems with point prevalence rates ranging between 12 and 20% (Cohen et al. 1993; Costello et al. 2005). Depression tends to affect a smaller number of youth, wherein 5–8% of adolescents and even fewer pre-adolescents meet criteria for a depressive disorder at any point in time (Angold and Costello 2001; Birmaher et al. 1996; Cohen et al. 1993). However, nearly 20% of youth may experience a depres- sive disorder by the end of adolescence (Lewinsohn et al. 1993). Both disorders are associated with severe disrup- tions in social, academic, and family functioning and have B. C. Chu (&) Á T. L. Harrison Department of Psychology, Rutgers, The State University of New Jersey, 152 Frelinghuysen Road, Piscataway, NJ 08854, USA e-mail: [email protected] 123 Clin Child Fam Psychol Rev (2007) 10:352–372 DOI 10.1007/s10567-007-0028-2

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Page 1: Disorder-specific Effects of CBT for Anxious and Depressed ...psych.colorado.edu/~willcutt/pdfs/Chu_2007.pdf · Disorder-specific Effects of CBT for Anxious ... A Meta-analysis

Disorder-specific Effects of CBT for Anxious and DepressedYouth: A Meta-analysis of Candidate Mediators of Change

Brian C. Chu Æ Tara L. Harrison

Published online: 6 November 2007

� Springer Science+Business Media, LLC 2007

Abstract The commonalities between anxiety and

depression have been discussed before, but few have

delineated the potentially different mechanisms through

which treatments work for these populations. The current

study conducted a comprehensive review of child and

adolescent randomized clinical trials that tested cognitive-

behavioral therapy (CBT) for anxiety or depression. All

studies were required to have assessed both treatment

outcomes and at least one theory-specific process target,

including behavioral, physiological, cognitive, and coping

variables. Using a meta-analytic approach, CBT demon-

strated positive treatment gains across anxiety, depression,

and general functioning outcomes. CBT for anxiety also

produced moderate to large effects across behavioral,

physiological, cognitive, and coping processes, with

behavioral targets demonstrating potentially the greatest

change. CBT for depression produced small effects for

cognitive processes but nonsignificant effects for behav-

ioral and coping variables. Findings were generally

consistent with CB theory but suggest potentially different

mediators in the treatment of anxiety and depression.

Results are discussed in terms of implications for mecha-

nisms research, theories of change, and treatment

development.

Keywords Child � Adolescent � Anxiety � Depression �CBT � Mechanisms of change

Introduction

The case for studying mediators of change in child and

adolescent treatment research has been made before

(Kazdin and Kendall 1998; Kazdin and Weisz 1998).

Identifying the critical ingredients and the mechanisms

through which treatments work is essential for maximizing

treatment efficacy, improving therapeutic techniques, and

improving methods for training therapists (Kazdin and

Nock 2003; Weersing and Weisz 2002). Despite the

importance of this research, there is a noted gap between

our knowledge of treatment outcomes and the processes

associated with those outcomes (Shirk 2005; Silverman

2006). The current review and meta-analysis will evaluate

the specific effects that cognitive-behavioral therapy (CBT)

produces in the treatment of anxious or depressed children

and adolescents.

Overlapping Features of Youth Anxiety and Depression

Combined, anxiety disorders such as generalized anxiety

disorder (GAD), separation anxiety disorder (SAD), social

phobia (SOC), and other phobic disorders are estimated to

represent the largest class of childhood emotional problems

with point prevalence rates ranging between 12 and 20%

(Cohen et al. 1993; Costello et al. 2005). Depression tends

to affect a smaller number of youth, wherein 5–8% of

adolescents and even fewer pre-adolescents meet criteria

for a depressive disorder at any point in time (Angold and

Costello 2001; Birmaher et al. 1996; Cohen et al. 1993).

However, nearly 20% of youth may experience a depres-

sive disorder by the end of adolescence (Lewinsohn et al.

1993). Both disorders are associated with severe disrup-

tions in social, academic, and family functioning and have

B. C. Chu (&) � T. L. Harrison

Department of Psychology, Rutgers, The State University of

New Jersey, 152 Frelinghuysen Road, Piscataway,

NJ 08854, USA

e-mail: [email protected]

123

Clin Child Fam Psychol Rev (2007) 10:352–372

DOI 10.1007/s10567-007-0028-2

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been connected with greater risk for more severe anxiety,

depression, and substance abuse in adulthood (Kendall et

al. 2003; Rohde et al. 1994).

There are several good reasons to examine anxiety,

depression, and their respective treatments together. A high

degree of co-occurrence has been established between

these disorders in both community and clinical samples. Up

to 69% of youth with primary anxiety have been diagnosed

with depression and up to 75% of depressed youth have

been diagnosed with an anxiety disorder (Angold et al.

1999; Brady and Kendall 1992; Kovacs 1990). Taxono-

metric approaches seeking to isolate uniquely identifying

symptom profiles have often found more commonalities

than differences (e.g., see Child Behavior Checklist

development; Achenbach 1991). Furthermore, longitudinal

studies have suggested a developmental relationship

between the disorders, in which problems in anxiety tend to

precede depression (Kessler et al. 1997; Kovacs et al.

1988). Of course, anxiety and depression are not com-

pletely overlapping phenomena. Several lines of research

(e.g., the tripartite theory; helplessness vs. hopelessness

theories) have identified cognitive and affective processes

that distinguish the disorders (Alloy et al. 1990; Barlow

et al. 1996; Clark and Watson 1991; Watson and Clark

1984), but overall, many commonalities exist.

Commonalities in Treatment Strategies and Treatment

Targets

A review of CBT programs targeting anxiety and depres-

sion reveals a number of similarities (Barlow et al. 2004;

Chorpita et al. 2002; Kazdin and Weisz 2003; Ollendick

and King 2000). As a whole, CBT aims to modify mal-

adaptive thinking and attitudes, increase skill sets, and

change unrewarding or avoidant behavioral patterns. Most

anxiety and depression treatments include general skills-

building strategies, such as self-monitoring, psychoeduca-

tion, problem-solving, social skills training, and reward

plans. The cognitive strategies for anxiety and depression

use many similar techniques, including identification of

thinking errors, Socratic questioning, and development of

coping thoughts. Even behaviorally oriented techniques

may be used to correct misperceptions and maladaptive

cognitions. For example, a child with social evaluation

concerns may be asked to give a speech in front of a mock

class. The in vivo exposure gives the youth an opportunity

to complete a difficult task and examine untested

assumptions about their abilities and the evaluations of

others. The specific target of cognitive restructuring may

vary across disorders (e.g., perceptions of threat and

unpredictability may be the target for anxious youth while

self-criticism and hopelessness may be emphasized in

depression), but replacing maladaptive thoughts with more

functional thinking is a common goal (Kendall et al. 2003;

Clarke et al. 2003; Weisz et al. 2003). Thus, successful

CBT would be expected to engender positive change in

cognitive processing including decreased negative auto-

matic thoughts, maladaptive attitudes and assumptions, and

decreased threat interpretations.

Behavioral techniques for treating anxiety and depres-

sion both make use of common learning and conditioning

principles. The primary behavioral target in anxiety treat-

ment is avoidance. Exposure tasks for anxious youth

assume that avoidance is prompted by emotional distress,

fear, and negative cognitions triggered by a feared event or

stimulus. Exposure therapy attempts to reduce avoidance

by having the child progressively work his or her way up a

graded fear hierarchy of feared situations while employing

coping skills or relaxation. Behavioral therapies for anxiety

also seek to reduce long-term physiological and subjective

fear responses to feared situations or challenges (Davis and

Ollendick 2005; Ollendick and King 1998). The specific

mechanisms through which exposures foster approach

behaviors are still a subject for debate (Craske and My-

stowski 2006; Foa and McNally 1996), but collectively,

successful CBT would be expected to be associated with

significant change across behavioral and physiological

processes (Davis and Ollendick 2005; Ollendick and King

1998).

Behavioral strategies for depression emphasize pleasant

activity scheduling and behavioral activation. Using these

strategies the therapist encourages activities that are indi-

vidually gratifying for the child to increase availability of

natural reinforcement in the child’s life and enhance the

child’s sensitivity to natural rewards (Lewinsohn and Graf

1973; Lewinsohn and Libet 1972). Recent conceptualiza-

tions of behavioral activation have also highlighted the role

of avoidance in depresso-typic behavior (Jacobson et al.

2001; Addis and Martell 2004). In this model, avoidance is

maintained in depression much like it is in anxiety;

avoidant behavior is triggered by a distressing event and

then is reinforced by the subsequent reduction in distress

even as it contributes to a number of secondary problems.

Continued avoidance perpetuates a cycle of inactivity,

withdrawal, and inertia that denies the child access or

opportunity to contact antidepressant sources of rein-

forcement (Jacobson et al. 2001). Thus, we would expect

successful CBT to be associated with increased activation,

frequency and enjoyment of pleasant activities, and a

possible decrease in avoidance. CBT also aims to teach

clients age appropriate skills, such as socialization and

social problem-solving skills. Increased skill sets are

expected to increase the child’s sense of mastery and the

likelihood that they will engage in social and pleasant

activities (Clarke et al. 2003; Weisz et al. 2003). Thus,

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CBT for youth with depression should be associated with

increased skill sets (e.g., social skills) associated with

behavioral activation.

Cognitive-behavioral interventions also aim to improve

coping skills or alter coping styles in anxious and depres-

sed youth (Prins and Ollendick 2003). Coping is a broad

term that embodies cognitive, behavioral, and physiologi-

cal processes and refers to how youth respond to stressful

events and challenges (Compas et al. 2001). Problem

solving, wishful thinking, cognitive avoidance, and rumi-

nation are coping strategies that primarily involve

cognitive processes. Avoidance, escape, and inaction are

types of behavioral coping strategies. Relaxation is a

coping strategy that primarily targets one’s physiological

state. Although many coping processes overlap with cog-

nitive and behavioral outcomes, investigators often

measure coping skills separately from dysfunctional

behavioral or cognitive styles, so it makes sense to consider

coping styles as unique targets of treatment. In general,

changes in coping style from avoidant to active strategies,

such as planning, thinking about solutions, and positive

cognitive restructuring, are associated with enhanced psy-

chological adjustment (Compas et al. 2001; Prins and

Ollendick 2003). Improvements in child and parent

reported coping efficacy have also been associated with

symptom improvement following CBT (Kendall 1994;

Kendall et al. 1997; Barrett et al. 1996).

Established Efficacy

Built on these sound theoretical principles and practices,

CBT has collectively documented impressive empirical

support for its treatment outcomes. In the treatment of

youth anxiety disorders, narrative and quantitative reviews

suggest that cognitive and behavioral approaches are

effective compared to no-treatment controls and alternative

treatments (Compton et al. 2002; Kaslow and Thompson

1998; Ollendick and King 1998). A number of individual

CBT programs also meet criteria as probably efficacious

using APA Task Force on Promotion and Dissemination of

Psychological Procedures guidelines (APA Task Force

1995; Ollendick and King 2000). In individual treatment

studies, CBT has compared favorably to wait-list and no-

treatment controls across a range of formats, including

individual child (e.g., Kendall 1994; Kendall et al. 1997),

family-focused (e.g., Barrett et al. 1996; Wood et al.

2006), and group (Flannery-Schroeder and Kendall 2000).

Similar CBT protocols have been adapted for adolescents

(Albano et al. 1995) and transported to school (Masia-

Warner et al. 2005) and medical center settings (Child

Anxiety Multimodal Study, in progress). The consistent

support for the efficacy of CBT suggests it is an appropriate

time to understand the basic mediators through which CBT

helps alleviate anxiety.

Outcome trials with depressed youth have also docu-

mented promising results for CBT. Two CBT programs

have been listed as a ‘‘probably efficacious’’ according to

APA Task Force criteria (Kaslow and Thompson 1998;

Ollendick and King 2000): Stark’s self-control treatment

(Stark et al. 1987) for child depression and Lewinsohn and

colleagues’ Coping with Depression course for adolescents

(Lewinsohn et al. 1990). Meta-analyses that have pooled

findings across clinical trials also have documented con-

sistent large effect sizes for CBT, ranging from 0.72 to 1.27

(Lewinsohn and Clarke 1999; Michael and Crowley 2002;

Reinecke et al. 1998). Recently, the relative strength of

CBT for depression has been questioned due to the success

of anti-depressant medications in comparative clinical tri-

als (Treatment for Adolescent Depression Study [TADS]

2004). Similarly, Weisz et al. (2006) recently completed

the most comprehensive meta-analysis to date and found

that the overall effects of psychotherapy for youth with

depression lagged significantly behind the psychotherapy

effects for other childhood disorders. In addition, Weisz

et al. demonstrated that cognitive-based therapies did not

produce superior overall outcomes compared to noncog-

nitive therapies in depressed youth. These findings suggest

that there is still substantial room for improvement in

psychological treatments for depression and that the effects

of cognitive therapies could benefit from further

investigation.

Together, the literature suggests that a comparison of

change mediators in efficacious treatments for anxious and

depressed youth would be timely and potentially revealing.

An analysis of the specific effects that CBT produces may

help identify its strengths as a treatment approach as well

as isolate areas in need of improvement. Such an analysis

may also delineate the underlying relationship between

anxiety and depression. However, to date, there has been

no direct comparison of the specific effects that CBT has

for anxious and depressed youth and whether similar or

distinctive mechanisms are responsible for observed treat-

ment outcomes.

State of Mechanisms Research in Youth CBT

There have been significant methodological and analytic

advances in mediator research (Kraemer et al. 2002;

MacKinnon et al. 2002; Shadish and Sweeney 1991). A

mediator specifies how (or the mechanism through which)

a given effect occurs (Baron and Kenny 1986; Holmbeck

1997; MacKinnon et al. 2002). The most common method

used to demonstrate a variable acts as a mediator has been

the ‘‘causal steps approach’’ (MacKinnon et al. 2002)

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based on Judd and Kenny (1981) and later elaborated on

by Baron and Kenny (1986). The Baron and Kenny model

outlines four specific conditions required to demonstrate

mediation, including that (a) the predictor must be sig-

nificantly associated with the mediator, (b) the predictor

must be significantly associated with the dependent

measure, (c) the mediator must be significantly associated

with the dependent variable, and (d) the impact of the

predictor on the dependent variable must be less after

controlling for the mediator (Baron and Kenny 1986;

Holmbeck 1997). Change in the mediator must also fol-

low the onset of the independent variable and precede

change in the dependent variable temporally (Judd and

Kenny 1981; Kazdin and Nock 2003). It then requires

several additional steps to establish a mediator as a

mechanism. Kraemer et al. (2002) remind us that ‘‘all

mechanisms are mediators but not all mediators are

mechanisms’’ (p. 878). However, demonstrating causality

is much more difficult than establishing mediator status.

Thus, the investment of time and effort to narrow the

search for causal factors by focusing first on a search for

mediators is worthwhile.

To conduct a broad review of the child clinical litera-

ture, Weersing and Weisz (2002) adapted Baron and

Kenny’s definition to create a framework for evaluating

mediating mechanisms across randomized clinical trials.

Most relevant to the current review, they re-labeled Baron

and Kenny’s (1986) criterion (b) the ‘‘Intervention-speci-

ficity test’’ and examined which treatments demonstrated a

significant relationship with prospective mediators. This

analysis tested whether treatment affected the mechanism

of action hypothesized to produce intervention effects (i.e.,

tested the hypothesized theory of change).

Using this framework, Weersing and Weisz (2002)

found that CBT did produce consistent overall treatment

outcomes for both anxiety and depression but there was

less information regarding the Intervention-Specificity

Test. For example, they reported that CBT was associated

with change in cognitive mediators in all anxiety studies,

and CBT was associated with change in cognitive and

behavioral mediators in most depression studies. However,

no specific effect sizes were provided to indicate the rela-

tive strength of these associations. ‘‘Box-score’’ type

narrative summaries of this sort are more sensitive to

individual study sample sizes and can result in misleading

conclusions (Beaman 1991; Lipsey and Wilson 2001). The

authors only reviewed the evidence for cognitive mediators

in the treatment of anxiety; they did not include a review of

behavioral, physiological, or coping variables. They also

did not report on the effect of depression treatments on

coping variables. Thus, the review supported the CB theory

of change for several common processes, but it did not

present data on other possible mediators and it did not

directly compare effects across diagnostic groups to

determine if CBT had differential impact across anxiety

and depression.

Three additional reviews explored similar issues. Prins

and Ollendick (2003) specifically reviewed the evidence

for cognitive and coping variables as mediators of CBT for

anxious youth. Similar to previous reviews, they found few

studies formerly testing mediation but many assessed pre-

to post-treatment outcomes of cognitive or coping process

(e.g., 44% of studies assessed cognitive change, 40% of

studies assessed coping attitudes or behaviors). Of those

studies that did measure process variables, CBT demon-

strated consistent effects. All controlled studies that

included either a coping or a cognitive variable reported

significant positive change from pre- to post-treatment.

Prins and Ollendick also calculated summary effect size

statistics. In randomized clinical trials comparing individ-

ual child CBT to a waitlist, treatment produced a small

effect in cognitive measures based on child report

(d = 0.36; range = 0.00–0.70). A moderate to large effect

in coping-related measures was found depending on whe-

ther child (d = 0.49) or parent (d = 0.99) report was

considered.

Prins and Ollendick (2003) did note that, in comparisons

of CBT to an alternate active treatment, CBT produced

significant pre- to post-changes in cognitive and coping

processes, but these differences were not significantly dif-

ferent from the control conditions. Thus, CBT may be

associated with cognitive changes, but such change may

not be uniquely related to CBT. In sum, the review helped

demonstrate at least partial support for the role of cognitive

and coping processes as possible mediators. Like Weersing

and Weisz (2002), this review did not examine CBT’s

effect on behavioral or physiological processes and did not

include depressive samples.

Davis and Ollendick (2005) conducted a comprehensive

review of CBT in producing specific change in a broader

set of processes associated with specific phobia, including

cognitive, behavioral, physiological, and subjective fear.

They reviewed 22 clinical trials that compared a behavioral

or cognitive treatment to either an active or passive control

condition. The majority of studies reviewed had included

some measure of behavioral and subjective fear change, but

many fewer measured cognitive or physiological change.

Based on a box score summary of the literature, there was

significant evidence that behavioral treatments produced

positive change in most behavioral and fear measures. This

finding held whether compared to either passive or active

controls. Thus, behavior and subjective fear appear to be

both reliably produced by, and specific to, behavioral

treatments in the treatment of specific phobias. Davis and

Ollendick did not provide effect size calculations to sum-

marize the magnitude of effect that treatment has on

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specific targets. The review also limited itself strictly to

treatment studies of specific phobia.

A final review conducted a meta-analysis evaluating the

overall outcomes of CBT for anxious and depressed youth

when compared against either a bona fide (active psycho-

logical treatment with a defined theory) or non-bona fide

(nonspecific active control) therapy (Spielmans et al.

2007). They divided outcome measures into dependent

variables that either directly measured anxiety or depres-

sion or measured some other outcome of interest. Their

analysis suggested that CBT did produce significant treat-

ment effects in both anxiety- and depression-specific and

more general outcomes when compared to active controls.

However, the analyses did not divide the anxiety and

depression measures into specific component processes of

cognitive, behavioral, coping, or physiological outcomes.

The Current Review

In the current report, we evaluate the specific effects that

CBT produces in the treatment of anxious or depressed

children and adolescents. Most previous meta-analyses

have reviewed overall treatment outcomes documenting

the general efficacy of CBT. Our review summarizes the

magnitudes of effect that CBT has on specific targets

related to the cognitive-behavioral theory of change,

including behavioral, physiological, cognitive, and coping

outcomes. Meta-analytic methods were used to summarize

and compare effect size (ES) calculations within and across

anxious and depressed study samples with special attention

paid to comparisons across diagnostic classes.

We hypothesized that CBT, when implemented with

anxious or depressed youth populations, would demon-

strate positive and significant effects for anxiety and

depression outcome measures. Based on previous reviews

(e.g., Weisz et al. 2006), we hypothesized that treatments

would produce larger effects for disorder-specific outcomes

(e.g., depression symptoms in CBT for depression) than

nonspecific outcomes (e.g., anxiety symptoms in CBT for

depression). Furthermore, based on the lower overall ES

values found for depression treatments in Weisz et al.

(2006), we also hypothesized that anxiety treatments would

produce larger effect sizes on treatment outcomes than

depression treatments.

In analyses focusing on specific behavioral, physiolog-

ical, cognitive, and coping change, we hypothesized that

CBT for anxiety would be associated with moderate to

large effects across all specific processes. We also

hypothesized that CBT for depression would produce

moderate to large effects in cognitive, behavioral, and

coping processes, but expected physiological processes to

be rarely assessed. We then compared magnitudes of ES

across process variables to determine if CBT had differ-

ential effects on specific targets. That is, within anxiety or

depression treatments, would mean ES values differ among

behavioral, physiological, cognitive, and coping outcomes?

These analyses were exploratory since we were not aware

of other attempts to make such a direct comparison.

Finally, we compared anxiety versus depression studies to

determine if CBT had differential effects on process out-

comes; these analyses were also exploratory given the

absence of previous comparisons.

Methods

Literature Review

Studies were obtained through reference trails and

computer index searches. We reviewed several recent,

comprehensive psychotherapy reviews and meta-analyses

(i.e., Compton et al. 2002; Kaslow and Thompson 1998;

Lewinsohn and Clarke 1999; Michael and Crowley

2002; Ollendick and King 1998; Prins and Ollendick

2003; Reinecke et al. 1998; Weersing and Weisz 2002;

Weisz et al. 2006) and included all relevant studies.

Studies were also obtained through computer index

searches using PsychINFO (1980–August, 2006) and

MEDLINE (1980–August, 2006) and by reference trails

that resulted from identified studies. Keywords used in

computer searches were: Depression, Major Depression,

Minor Depression, Dysthymia, Anxiety, Anxiety Disor-

ders, Generalized Anxiety Disorder, Separation Anxiety

Disorder, Social Phobia, CBT, cognitive-behavioral

therapy, cognitive therapy, behavior therapy, exposure

therapy, and behavioral activation. The auto-explode

option was used in computer searches so that all relevant

topics within the broader categories were searched as

well. Searches were limited to populations between ages

6 and 18 years.

Studies were obtained and included if they met the

following criteria: (a) study participants were selected for

a clinical diagnosis of anxiety or clinically significant

depression; (b) random assignment to treatment condi-

tions was used; (c) at least one of the treatment

conditions was identified as a behavioral, cognitive, or

cognitive-behavioral intervention (the comparison condi-

tions could be either a passive control or alternate

treatment); (d) sample age range was between 6 and

18 years old; and (e) the study was published in an

English language, peer-reviewed journal. Studies had to

report posttreatment data (means and standard deviation)

for at least one outcome measure that assessed anxiety or

depression. Studies also had to report data for at least

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one cognitive, coping, behavioral, or physiological target

at posttreatment (studies did not have to report data for

all four process categories). Citations of included studies

appear in the reference list with asterisks.

Studies were not included if they explicitly described

the intervention as a prevention program. Studies were

not included if analyses only compared one CBT con-

dition against another CBT condition (e.g., individual

CBT vs. CBT + parent involvement), because the

study’s goal was to compare CBT versus active or

passive controls. Studies that targeted school refusal

were included. Studies were not included if the primary

treatment target was Specific Phobia, Obsessive-Com-

pulsive Disorder, Post-Traumatic Stress Disorder, Panic

Disorder, or test anxiety. CBT interventions were not

included if treatment format was primarily computer-

based or virtual reality. Finally, studies were not

included if the only CBT condition was a combined

CBT plus pharmacotherapy condition.

Study Coding Procedures

Studies were coded to identify (a) sample characteristics,

(b) treatment and design characteristics, (c) anxiety and

depression outcome measures used, and (d) mediator

(process) measures used. Treatment outcome measures

were included for ES coding if they assessed anxiety or

depression symptoms (e.g., parent or child-report ques-

tionnaires), diagnosis (e.g., structured interview), or

general functioning or improvement (e.g., Global Assess-

ment of Functioning scales, Clinical Global Improvement

scales). Process measures were included if they targeted

behavioral, physiological, cognitive, or coping constructs.

These could include parent- and child-report question-

naires, judge-rated observations, and independent reports

(e.g., school-reported attendance records, diary reports of

attended social events).

Two raters (the authors) independently coded 14 studies

each. To assess interrater reliability, both raters double

coded eight (28.6%) of the studies. Raters demonstrated

excellent 94.6% (k = 0.89) agreement in identifying which

outcome and process measures should be included for

coding. Intraclass correlation coefficients (ICC) were cal-

culated to assess rater reliability in coding means and

standard deviations and in calculating ESs. Raters dem-

onstrated excellent reliability in coding means

(ICC = 1.00, p \ .001) and standard deviations (ICC =

0.99, p \ 0.001) and in calculating ES scores from raw

data (ICC = 0.98, p \ 0.001). Raters were exceptionally

reliable in coding raw data from studies and calculating ES

scores.

Statistical Analyses

Cohen’s d (1988) was the measure of effect size. Cohen’s

d is the mean difference between the mean outcome in

the treatment group and the mean outcome in the control

group divided by the pooled (within-group) standard

deviation. In studies that included more than one CBT

condition (e.g., individual CBT, individual + parent

CBT), each intervention was compared to the control

condition (e.g., WL, educational support). All ES values

were corrected for small sample bias (Hedges and Olkin

1985, p. 81, Equation 10) and then pooled up to the level

of treatment. This permitted an evaluation of effect size

for an average CBT condition. ES values were then

weighted by the inverse of its variance, adjusting for

varying sample sizes and heterogeneity of variance across

studies (Hedges and Olkin 1985; Lipsey and Wilson

2001).

As a final step, when calculating mean ES values, a Q-

statistic was calculated to test the assumption that all ES

values estimated the same population (i.e., homogeneity in

ES distributions; Lipsey and Wilson 2001). When homo-

geneity is rejected, this indicates the variability among the

study effect sizes are greater than what is likely to have

resulted from subject-level sampling error alone. In these

cases, we adopted a random effects model which accounts

for random variability at both the study-level (studies

sampled from a population of studies) and the subject-level

(subjects in each study sampled from a population of

studies). This model uses a different inverse variance

weight than the fixed effects model (used when effect sizes

represent a homogeneous distribution). All ES means

reported hereafter are weighted least square effect sizes

based on the appropriate model (either random or fixed

effects) depending on the results of the Q-statistic. To

interpret ESs, we used Cohen’s (1992) definitions in which

an ES of 0.20 indicates a small effect, 0.50 a medium

effect, and 0.80 a large effect.

To compare mean ES values with zero, we used SPSS

macros that generate z tests based on the absolute value of

the mean ES divided by the standard error of the mean

ES (Lipsey and Wilson 2001; Wilson 2003). Consistent

with previous meta-analyses (e.g., Weisz et al. 2006), we

used paired t-tests to compare ES values of conceptually

different measures obtained from the same set of studies

(e.g., behavioral vs. physiological vs. cognitive vs. coping

ES means). Paired t-tests acknowledge dependencies

among the variables resulting from ESs calculated from

the same study samples. To compare mutually exclusive

categories of studies (e.g., Anxiety vs. Depression stud-

ies), we used a Q-statistic analog to analysis of variance

(Lipsey and Wilson 2001; Wilson 2003). In this analysis,

if the between-category variance is significant, then the

Clin Child Fam Psychol Rev (2007) 10:352–372 357

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mean ES values across groups differ by more than sam-

pling error.

Results

Descriptive Characteristics of Reviewed Studies

The final sample consisted of 14 anxiety studies repre-

senting 22 CBT treatment conditions, and 14 depression

studies representing 20 CBT conditions. Of the anxiety

studies, nine studies used a waitlist control and five com-

pared CBT to an active control condition (e.g., educational

support, nonspecific treatment). Six anxiety studies inclu-

ded multiple forms of CBT (e.g., individual, group, or

parent condition). Of the depression studies, eight studies

used a waitlist or no-treatment control and six compared

CBT to an active treatment condition (e.g., Life skills,

nonspecific support). Four depression studies included

multiple forms of CBT (e.g., individual vs. family-based;

self-control vs. behavioral problem solving). Descriptive

information about study design, participants, and treat-

ments are reported in Tables 1 and 2.

Tables 1 and 2 also report the assessment measures used

to assess behavioral, physiological, cognitive, and coping

processes in anxiety and depression studies. Over 71%

(n = 10) of anxiety studies and 50% (n = 7) of depression

studies included an assessment of behavioral processes. In

the anxiety studies, a diverse range of methods were used

to assess behavioral processes, including behavioral

observation tasks (e.g., independent coding of a speech

task; choice of avoidant solutions during a family interac-

tion task), parent- or child-report measures (e.g., Friendship

measure; Social Skills Questionnaire), and subscales of

larger anxiety measures (e.g., Liebowitz Social Anxiety

Scale—social avoidance and performance subscales).

Behavioral observations were not used in depression

studies, but parent and youth report of pleasant activities

(e.g., Pleasant Events Scale; CBCL—social activities

subscale) and social skills (e.g., Social Adjustment Scale;

Social Adjustment Inventory for Children and Adolescents)

were common.

Only a small percentage of anxiety studies, 21.4%

(n = 3), and no depression studies assessed any physio-

logical process. Physiological processes were assessed

exclusively with subscales of larger anxiety measures (e.g.,

CBCL—health concerns subscale; State-Trait Anxiety

Inventory—somatic subscale). No direct measures of

physiology (e.g., heart rate, galvanic skin response) were

used.

Cognitive processes were consistently assessed, with

71.4% (n = 10) of anxiety studies and 78.6% (n = 11) of

depression studies including some cognitive assessment.

Youth self-report was the primary mode of assessment in

both anxiety and depression studies and assessed various

constructs, such as self-esteem (e.g., Rosenberg Self

Esteem Scale), self-concept (Piers-Harris Child Self-Con-

cept), negative affectivity self-statements (e.g., NASSQ),

maladaptive beliefs (e.g., Cognitive Bias Questionnaire;

DAS), and distorted cognitions (ATQ; CNCEQ; SAS—

Fear of Negative Evaluation subscale). One family inter-

action task was used (Barrett et al. 1996) in which threat

interpretations were assessed before and after a family

discussion of an ambiguous situation.

Finally, 42.9% (n = 6) of anxiety studies and few

depression studies, 14.3% (n = 2), included an assessment

of coping. In anxiety studies, coping was assessed pri-

marily with youth-report measures, assessing either general

strategies (e.g., Self-Efficacy Questionnaire; Children’s

Coping Strategies Checklist) or coping in specific situa-

tions (Coping Questionnaire—child and parent versions).

One study (Beidel et al. 2000) coded percentage of coping

statements identified in daily diary entries. One measure,

the adolescent- and parent-report Issues Checklist, was

used in the two depression studies.

Assessment of treatment outcomes (diagnosis, symp-

tom) was consistent with measurement typically found in

randomized clinical trials (RCTs). Diagnoses were deter-

mined using clinician-administered semi-structured

interviews (e.g., Anxiety Disorders Interview Schedule,

Kiddie-SADS, Hamilton Depression Rating Scale), and

symptom ratings of anxiety and depression were typically

evaluated with paper-and-pencil questionnaires using

child-report, parent-, and teacher-report. We also included

assessments of broad-based general functioning that were

not captured by specific anxiety and depression measures.

These included broadband scales (e.g., Child Behavior

Checklist—Internalizing and Anxiety/Depression scales)

and clinician rated global severity or improvement mea-

sures (e.g., Children’s Global Assessment Scale, Global

Assessment of Functioning, Clinical Global Impression).

Of note, anxiety studies more frequently assessed depres-

sion (78.6%, n = 11) and general functioning (64.3%,

n = 9) outcomes than did depression studies where only

35.7% (n = 5) assessed anxiety and 35.7% (n = 5)

assessed general functioning outcomes. (To conserve

archival space, outcome measures are not presented in a

table here. A complete list of anxiety, depression, and

general functioning measures included in analyses is

available from the authors.)

Relevant to the discussion of mechanisms, three

depression studies included some analysis of mediation

(Ackerson et al. 1998; Kaufman et al. 2005; Kolko et al.

2000). None of the identified anxiety studies reported

mediation analyses as part of the principal outcome study,

but one study (Treadwell and Kendall 1996) later reported

358 Clin Child Fam Psychol Rev (2007) 10:352–372

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Ta

ble

1D

escr

ipti

ve

char

acte

rist

ics

of

stu

die

sev

alu

atin

gC

BT

for

yo

uth

anx

iety

(n=

14

)

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dy

Par

tici

pan

tsS

elec

tio

ncr

iter

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reat

men

tsT

xd

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nit

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mea

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mea

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s

Bar

rett

etal

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99

6)

n=

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;7

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AD

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OP

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AD

CB

Tv

s.C

BT

+F

amM

gm

tv

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12

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–80

min

FE

AR

-AS

;C

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vo

idF

EA

R-T

I

Bei

del

etal

.(2

00

0)

n=

50

;8

+1

2y

oS

OP

SE

T-C

vs.

No

nsp

ecT

x(T

estb

ust

ers)

24

ss,

60

–90

min

,1

2w

eeks

BO

:S

oci

alta

sk,

read

-al

oud

effe

ctiv

enes

s:se

lf&

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n=

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CB

Tv

s.G

rpC

BT

vs.

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18

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1h

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al;

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CS

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SP

PC

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cial

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lag

her

etal

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00

4)

n=

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–1

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Gro

up

CB

Tv

s.W

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3h

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ks

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cial

com

pet

ence

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tivit

ies,

sch

ool

Gar

cia-

Lo

pez

etal

.(2

00

2)

n=

59

;1

5–

17

yo

SO

PS

ET

-Av

s.C

BG

T-

Av

s.IA

FS

Gv

s.W

L

SE

T=

19

ss,

CB

GT

=1

6ss

,IA

FS

G=

12

ss

IS;

EH

SP

A;

PR

CS

RS

ES

Ken

dal

l(1

99

4)

n=

47

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–1

3y

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AD

,S

AD

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OP

CB

Tv

s.W

L1

6ss

BO

—sp

eech

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tal

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re;

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-P-

soci

alC

BC

L-P

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lth

NA

SS

QC

Q-C

Ken

dal

let

al.

(19

97)

n=

94

;9

–1

3y

oG

AD

,S

AD

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OP

CB

Tv

s.W

L1

6ss

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—sp

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conta

ct

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get

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(19

98)

n=

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;5

–1

5y

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cho

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refu

sal

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Tv

s.W

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ss,

50

min

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wee

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tet

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(19

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n=

41

;6

–1

7y

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ph

obia

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Tv

s.ed

uca

tio

nal

sup

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etal

.(2

00

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n=

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choo

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vs.

WL

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fav

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Ev

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zet

al.

(19

99)

n=

62

;7

–1

2y

oA

nx

Dx

CB

T-P

ar+

Ch

vs.

CB

T-C

hv

s.C

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vs.

WL

90

min

,1

2w

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tiv

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ris

etal

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00

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n=

24

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2y

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AD

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pin

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xv

s.n

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re)

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ver

man

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99

9)

n=

10

4;

6–

16

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tro

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EQ

Clin Child Fam Psychol Rev (2007) 10:352–372 359

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analysis for participants included in previous research

(Kendall 1994; Kendall et al. 1997). Further, only one

anxiety study (Kendall et al. 1997) and one depression

study (Kolko et al. 2000) assessed process measures and

outcomes at more time points than just at pre- and post-

treatment.

Effect of CBT on Anxiety and Depression Outcomes

To show that the current sample resembled studies in

previous reviews, effect sizes of treatment outcome were

calculated. CBT produced moderate effect sizes across

anxiety, depression, and general functioning outcomes (see

Table 3). Across the 14 anxiety studies, mean ES for

anxiety outcomes was 0.64 (SD = 0.38; range = 0.18–

1.42) and significantly different from zero (z = 9.37,

p \ 0.001). Mean ES for depression outcomes was 0.55

(SD = 0.23; range = -0.06–0.92), and mean ES for

general functioning was 0.45 (SD = 0.53; range = -

0.54–1.72). Depression and general functioning ESs were

both significantly different from zero, p \ .001 and

p \ .01, respectively.

Similar treatment effects were found when CBT was

compared to wait-list control, but effects were lower when

compared to an alternate treatment. In the nine anxiety

studies where a waitlist was the comparison, CBT pro-

duced moderate mean ESs in anxiety (ES = 0.74,

p \ 0.001), depression (ES = 0.54, p \ 0.001), and gen-

eral functioning (ES = 0.66, p \ 0.001). In the five studies

that compared CBT to an active control, CBT produced

small to moderate mean ESs in anxiety (ES = 0.37,

p \ 0.01), depression (ES = 0.57, p \ 0.001), and general

functioning (ES = 0.24, p = n.s.).

Across the 14 depression studies, CBT produced vari-

able results in treatment outcomes (see Table 3). Mean ES

for depression outcomes was 0.60 (SD = 0.48; range = -

0.51–1.69) and significantly different from zero (z = 5.24,

p \ 0.001). A small effect for anxiety outcomes was

found; mean ES was 0.28 (SD = 0.44; range = -0.25–

1.62), which was significantly different from zero

(z = 1.95, p = 0.05). Mean ES for general functioning

was small, 0.46 (SD = 0.46; range = -0.19–1.05), and

significantly different from zero (z = 2.29, p \ 0.05).

A similar pattern of effects was found when CBT was

compared to no-treatment or wait-list controls, but effects

appeared slightly higher than the overall sample. In the

eight studies where a waitlist or no treatment was the

comparison, CBT produced a large mean ES in depression

outcomes (ES = 0.87, p \ 0.001), but small ESs for anx-

iety (ES = 0.40, p = n.s.) and general functioning

outcomes (ES = 0.46, p = n.s.) that were nonsignificantly

different from zero. In the six studies that compared CBTTa

ble

1co

nti

nu

ed

Stu

dy

Par

tici

pan

tsS

elec

tio

ncr

iter

iaT

reat

men

tsT

xd

ura

tio

nB

ehav

iora

lm

easu

reP

hy

sio

mea

sure

sC

og

nit

ive

mea

sure

sC

op

ing

mea

sure

s

Sp

ence

etal

.(2

00

0)

n=

50

;7

–1

4y

oS

OP

CB

T+

Par

vs.

CB

Tv

s.W

L1

2ss

,2

bo

ost

erB

AT

-CR

;S

CQ

-P;

SS

Q-P

;S

cho

ol

ob

sra

ting

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cial

SW

Q-P

U

No

te:

yo

=y

ears

old

;O

AD

=o

ver

anx

iou

sd

iso

rder

;S

OP

=so

cial

ph

ob

ia;

SA

D=

sep

arat

ion

anx

iety

dis

ord

er;

GA

D=

gen

eral

ized

anx

iety

dis

ord

er;

SE

T-C

=so

cial

effe

ctiv

enes

sth

erap

y;

IAF

SG

=th

erap

yfo

rad

ole

scen

tsw

ith

gen

eral

ized

soci

alp

ho

bia

;ss

=se

ssio

ns.

Mea

sure

sa

rep

rese

nte

din

alp

ha

bet

ica

lo

rder

:B

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-CR

=re

vis

edb

ehav

ior

asse

rtiv

enes

ste

stfo

rch

ild

ren

;

BO

=b

ehav

iora

lo

bse

rvat

ion

s;C

BC

L=

chil

db

ehav

ior

chec

kli

st—

soci

alco

mp

eten

ce,

acti

vit

ies,

sch

oo

l,h

ealt

hsu

bsc

ales

,p

aren

tv

ersi

on

;C

CS

C=

chil

dre

n’s

cop

ing

stra

teg

ies

chec

kli

st—

acti

ve,

avo

idan

t,d

istr

acti

on

,su

pp

ort

sub

scal

e;C

E=

clin

ical

eval

uat

ion

,av

oid

ant

beh

avio

r;C

NC

EQ

=ch

ild

ren

’sn

egat

ive

cog

nit

ive

erro

rq

ues

tio

nn

aire

;C

Q-C

/P=

cop

ing

qu

esti

on

nai

re,

chil

d,

par

ent

ver

sio

ns;

EH

SP

A=

soci

alsk

ills

scal

efo

rad

ole

scen

ts;

FE

AR

-AS

=F

EA

Rta

sk-a

vo

idan

tso

luti

on

s;F

EA

R-T

I=

FE

AR

task

-th

reat

inte

rpre

tati

on

;F

M-C

/P=

frie

nd

ship

mea

sure

,ch

ild

,

par

ent

ver

sio

ns;

IS=

inad

apta

tio

nsc

ale;

LS

AS

-CA

=L

ieb

ow

itz

soci

alan

xie

tysc

ale

for

chil

dre

nan

dad

ole

scen

ts—

soci

alav

oid

ance

,p

erfo

rman

cesu

bsc

ales

;N

AS

SQ

=ch

ild

ren

’sn

egat

ive

affe

ctiv

ity

self

stat

emen

tq

ues

tio

nn

aire

;P

RC

S=

pu

bli

cre

po

rto

fco

nfi

den

ceas

spea

ker

;P

RS

CC

=p

aren

tra

tin

gsc

ale

of

chil

dco

mp

eten

ce—

soci

alsc

ale;

PS

WQ

-C=

Pen

nst

ate

wo

rry

qu

esti

on

nai

refo

rch

ild

ren

;R

CM

AS

=re

vis

edch

ild

ren

’sm

anif

est

anx

iety

scal

e—p

hy

sio

log

ical

,w

orr

y,

ov

erse

nsi

tiv

ity

,so

cial

con

cern

s,co

nce

ntr

atio

nsu

bsc

ales

;R

SE

S=

Ro

sen

ber

gse

lf-

este

emsc

ale;

SA

S-A

/P-F

NE

=so

cial

anx

iety

scal

e-fe

aro

fn

egat

ive

eval

uat

ion

sub

scal

e,ad

ole

scen

t,p

aren

tv

ersi

on

s;S

OC

S-P

=so

cial

acti

vit

ies

scal

e;S

CQ

-P=

soci

alco

mp

eten

ceq

ues

-

tio

nn

aire

;S

EQ

-SS

=se

lf-e

ffica

cyq

ues

tio

nn

aire

for

sch

oo

lsi

tuat

ion

s;S

PP

C=

Har

ter’

sse

lfp

erce

pti

on

pro

file

for

chil

d—

soci

alac

cep

tan

cesu

bsc

ale;

SS

Q-P

=so

cial

skil

lsq

ues

tio

nn

aire

;

ST

AIC

-M=

mo

difi

edst

ate-

trai

tan

xie

tyin

ven

tory

for

chil

dre

n-

som

atic

,co

gn

itiv

esu

bsc

ales

;S

WQ

-PU

=so

cial

wo

rrie

sq

ues

tio

nn

aire

-pu

pil

360 Clin Child Fam Psychol Rev (2007) 10:352–372

123

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Ta

ble

2D

escr

ipti

ve

char

acte

rist

ics

of

stu

die

sev

alu

atin

gC

BT

for

yo

uth

dep

ress

ion

(n=

14

)

Stu

dy

Par

tici

pan

tsS

elec

tio

ncr

iter

iaT

reat

men

tsT

xd

ura

tio

nB

ehav

iora

l

mea

sure

s

Co

gn

itiv

e

mea

sure

s

Co

pin

g

mea

sure

s

Ack

erso

net

al.

(19

98)

n=

22

;7

–1

2th

gra

de

CD

I&

HR

SD

C1

0C

og

nit

ive

bib

lio

ther

apy

vs.

WL

4w

eek

sA

TQ

;D

AS

;C

og

BT

DeC

uy

per

etal

.(2

00

4)

n=

20

;9

–1

1y

oC

DI

C1

1;

CB

CL

A/D

TC

63

;D

SM

-III

-R

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(19

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n=

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n=

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n=

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ence

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n=

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ssel

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99)

n=

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nce

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S=

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sen

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tin

ven

tory

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ts,p

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cial

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r

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ts;

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just

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po

rt;

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self

este

emin

ven

tory

,ch

ild

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aren

tv

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on

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Jack

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emsc

ale

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to an active control, CBT produced small mean ESs in

depression (ES = 0.29, p \ 0.05), anxiety (ES = 0.19,

p = n.s.), and general functioning (ES = 0.48, p = n.s.).

The inconsistency between magnitude of ES and statistical

significance testing reflects the variability among the small

number of studies assessing anxiety and general function-

ing outcomes.

Specific Processes Change in CBT for Anxiety

CBT for anxiety was associated with consistent moderate to

large mean ES values across behavioral, physiological,

cognitive, and coping processes (see Table 3). Across the

14 anxiety studies, CBT produced a large mean ES for

behavioral processes, ES = 1.02 (SD = 0.95; range =

0.002–3.59; z = 4.09) and moderate mean ESs for physi-

ological processes, ES = 0.49 (SD = 0.35; range = 0.29–

1.25; z = 3.79), cognitive processes, ES = 0.50 (SD =

0.46; range = 0.00–1.77; z = 4.19), and coping, ES =

0.73 (SD = 0.45; range = 0.12–1.65; z = 4.46). All mean

ESs were significantly different from zero (p \ 0.001).

We conducted six paired t-tests to compare mean ESs

across process variables (e.g., behavioral vs. physiological;

behavioral vs. cognitive; behavioral vs. coping; etc.). For

each analysis, only studies including both process variables

were included. In the anxiety studies, two comparisons

approached significance. A paired t-test comparing physi-

ological processes (ES = 0.54, SD = 0.41) and cognitive

processes (ES = 0.20, SD = 0.23) was marginally signif-

icant, t(4) = 2.76, p = 0.051, and a comparison of coping

(ES = 0.61, SD = 0.49) and cognitive processes (ES =

0.19, SD = 0.23) approached significance, t(4) = -2.48,

p = 0.07. In the seven studies (11 treatment comparisons)

that assessed both behavioral and cognitive processes,

mean behavioral ES (1.25, SD = 1.13) was larger than

mean cognitive ES (0.74, SD = 0.55), but this difference

was not statistically significant, t(10) = 1.47, p = 0.17.

Specific Processes Change in CBT in Depression

In contrast to anxiety studies, CBT for depression was

associated with a small but significant effect in cognitive

processes but not in behavioral or coping processes (see

Table 3). Across the 14 depression studies, CBT was

associated with a small cognitive effect, ES = 0.35

(SD = 0.49; range = -0.64–1.36) that was significantly

different from zero, z = 2.64, p \ 0.01. Mean ES for

behavioral processes was 0.01 (SD = 0.26; range = -

0.38–0.39; z = 0.03) and 0.05 (SD = 0.06; range = -

0.03–0.14; z = 0.31) for coping processes. Neither

behavioral nor coping ESs were significantly different from

zero (p = n.s.). No depression studies reported assessment

of physiological processes.

We attempted three paired t-tests to compare mean

behavioral, cognitive, and coping ESs (i.e., behavioral vs.

cognitive; behavioral vs. coping; cognitive vs. coping).

Table 3 Weighted mean effect sizes (ES) for process variables and symptom outcomes

Behavior ES Physiology ES Cognitive ES Coping ES Anxiety ES Depression ES GF ES

All anxiety studies

Mean ES 1.02* 0.49* 0.50* 0.73* 0.64* 0.55* 0.52**

n (Treatments) 16 5 16 9 22 16 12

Anx: CBT vs. WL

Mean ES 1.08* 0.48* 0.58* 0.77* 0.74* 0.54* 0.66*

n (Treatments) 13 4 12 8 17 12 8

Anx: CBT vs. Active Ctrl

Mean ES 0.78* 0.56 0.35*** 0.48 0.37** 0.57* 0.24

n (Treatments) 3 1 4 1 5 4 4

All depression studies

Mean ES 0.01 – 0.35** 0.05 0.28*** 0.60* 0.46***

n (Treatments) 8 16 3 7 20 7

Dep: CBT vs. WL

Mean ES 0.18 – 0.62* 0.06 0.40 0.87* 0.46

n (Treatments) 4 10 2 5 13 5

Dep: CBT vs. Active Ctrl

Mean ES -0.05 – 0.04 0.04 0.19 0.29** 0.48

n (Treatments) 4 6 1 2 7 2

Note: GF = General Functioning; Mean ESs are weighted least squares effect sizes; *p \ 0.001; **p \ 0.01; ***p \ 0.05

362 Clin Child Fam Psychol Rev (2007) 10:352–372

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Only one depression study assessed both behavioral and

coping processes, and only one study assessed both cog-

nitive and coping variables, so paired t-tests could not be

performed. In studies assessing both behavioral and cog-

nitive processes (n = 5 studies; six treatment

comparisons), no significant differences were found,

t(5) = -1.09, p = 0.33. In these studies, mean behavioral

ES was -0.01 (SD = 0.29) and mean cognitive ES was

0.14 (SD = 0.42).

Does CBT Have Different Effects on Process or

Outcomes in Anxious Versus Depressed Samples?

To compare mutually exclusive categories of studies (i.e.,

anxiety vs. depression studies), we used a Q-statistic analog

to analysis of variance (Lipsey and Wilson 2001; Wilson

2003). If the between-category variance is significant, then

the mean ESs across groups differ by more than sampling

error. The Q-statistic is distributed as a chi-square with k–j

degrees of freedom, where k is the number of ESs (Hedges

and Olkin 1985), and j is the number of groups. We con-

ducted all analyses using maximum likelihood, random

effects models weighted by the inverse of the variance.

We compared the 10 anxiety studies (16 treatments) against

the seven depression studies (eight treatments) that assessed

behavioral processes. Mean behavioral ES was significantly

greater in studies testing CBT for anxiety (ES = 1.01, SE =

0.21) than in studies testing CBT for depression (ES = 0.05,

SE = 0.29), Q(1, 22) = 7.13, p \ 0.01. To compare differ-

ential effects on cognitive processes, we compared the 10

anxiety studies (16 treatments) to the 12 depression studies (16

treatments) that assessed cognitive outcomes. Anxiety and

depression studies were nonsignificantly different in mean

cognitive ES, Q(1, 30) = 0.84, p = 0.36. Mean cognitive ES

for anxiety samples was 0.50 (SE = 0.12) and 0.34 (SE =

0.34) for depressed samples. Anxiety studies (nine treatments)

did produce significantly greater effects on coping processes

than depression studies (three treatments), Q(1, 10) = 7.27,

p \ 0.01. Mean coping ES for anxiety samples was 0.71

(SE = 0.13) and 0.05 (SE = 0.21) for depressed samples. We

also compared anxiety and depression studies on treatment

outcomes and found a significant difference between anxiety

and depression studies on mean anxiety ES, Q(1, 27) = 3.97,

p \ 0.05, but not on depression or general functioning mean

ESs. Mean anxiety ES for anxious youth was 0.66 (SE = 0.08)

and 0.30 (SE = 0.16) for depressed youth.

Discussion

We conducted a comprehensive search to identify pub-

lished RCTs that tested CBT for anxiety or depression that

included measurement of both treatment and process out-

comes. Our review is unique in its attempt to summarize

the magnitudes of effect that CBT has on specific theory-

related targets, including behavioral, physiological, cogni-

tive, and coping outcomes. Using a meta-analytic

approach, analyses produced both anticipated and surpris-

ing results.

Assessment of Process and Outcomes

We identified 14 anxiety studies and 14 depression studies

that met our criteria. In general, these studies represent a

moderate proportion of all RCTs testing CBT for youth

internalizing problems. Weisz et al. (2006), for example,

identified 25 total clinical trials between 1980 and 2004

testing CBT for depression. Compton et al. (2002) and

Prins and Ollendick (2003) identified between 16 and 18

CBT trials for anxiety using various criteria. In our own

search, we identified 11 other anxiety trials and five

depression studies that met all other inclusion criteria

except for reporting data for a process variable. Thus, a

substantial proportion of our most rigorous clinical trials

does not routinely assess and/or report process outcomes.

This sadly represents missed opportunities to examine

important treatment effects.

Further, only four studies reported formal tests of

mediation and two studies assessed processes or outcomes

at timepoints other than at pre- and post-treatment. As

discussed earlier, both statistical mediation and temporal

precedence must be demonstrated to establish a variable as

a mediator (Judd and Kenny 1981; Kazdin and Nock 2003).

That is, change in the mediator must follow initiation of the

treatment but precede change in the outcome. Without

repeated assessment of process and outcome throughout

therapy, this relationship cannot be demonstrated. Signifi-

cant change in how RCTs are designed and conducted is

necessary before questions about mediation can be

addressed.

In absence of formal mediation tests, we hoped to

identify potential mediators by evaluating CBT’s effect on

specific processes. Of the 14 anxiety studies identified for

this review, process measurement was reasonably well

represented. The majority of studies reported behavioral

(71%) or cognitive (71%) outcomes, but fewer reported

physiological (21%) or coping (42%) outcomes. Of the 14

depression studies, the large majority reported cognitive

outcomes (78%), fewer assessed behavioral (50%), and

coping (14%) processes, and no studies assessed physio-

logical outcomes. These results highlight revealing trends

in the outcomes literature. Cognitive and behavioral pro-

cesses were regularly assessed in anxiety studies, but

physiological outcomes were only rarely reported. This is

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surprising given the central role attributed to habituation

and distress tolerance in exposure-based treatments (Craske

and Mystkowski 2006). Likewise, cognitive measures were

routinely assessed in depression studies, but only half the

studies measured a behavioral outcome and a small fraction

of studies assessed coping. This is surprising given the

central roles that behavioral activation and skill-building

have in CBT for depression (Clarke et al. 2003; Jacobson

et al. 2001; Weisz et al. 2003). The range of different

measures was also limited in several categories. Three

different measures were used to assess physiological pro-

cesses in anxiety studies and only one measure was used to

assess coping in depression studies.

These trends could reflect unstated investigator bias

toward particular theories of change, such that anxiety

researchers view behavioral and cognitive change as more

central to outcomes than physiological and coping change.

Depression researchers may believe that cognitive change

represents the critical process to monitor. Pragmatic con-

siderations may overlap with theoretical leanings. In the

face of multiple design choices, limited resources, and a

desire to minimize participant burden, investigators likely

prioritize the outcomes they believe most central to their

theory of change or those variables they believe would

likely evidence the greatest association with treatment.

These measurement trends may also reflect the relative

challenges in assessing various constructs. In the case of

depression-focused treatments, it may be less clear what

behavioral outcomes are expected or how to operationalize

them for the purpose of assessment. In depression studies,

behavioral outcomes were primarily assessed by child- or

parent-reported questionnaires of pleasant activities or

social skills. Problem-solving skills, communication skills,

and access to and use of social support are other important

outcomes, but they may be more challenging to accurately

assess. Direct behavioral observation may seem more

appropriate for assessing markers of anxiety, which

explains their greater use in anxiety trials. A youth with a

fear of a specific stimulus or situation can participate in a

BAT and be assessed for approach and avoidance

behaviors.

A comparable tool for assessing behavioral indices in

depression is less apparent, but anxiety studies may be able

to provide relevant models. Several studies used a speech

task and developed a coding system for assessing behav-

ioral indicators of anxiety (e.g., fidgeting, poor eye contact,

poor initiation of speech topics; Kendall 1994; Kendall

et al. 1997). A similar task could be adapted to evaluate

behavior change in depressed youth. For instance, the

Primary and Secondary Control Enhancement Treatment

developed by Weisz et al. (1997) includes a module that

helps the child identify their negative self-presentation

styles and then provides practice in presenting a more

‘‘positive’’ self. A behavioral task could be developed to

assess change in the interpersonal styles of depressed youth

(e.g., poor eye contact, flat affect, paucity of speech, neg-

ative content). Other anxiety studies employ a family

discussion task in which the youth’s decision-making

process is evaluated (e.g., threat interpretations, choice of

avoidant solutions; Barrett et al. 1996). An equivalent

family discussion could be developed to test a depressed

youth’s skill level at posttreatment. Does the youth dem-

onstrate greater use of problem solving or communication

skills or greater pro-social or proactive decision-making?

Treatment Outcomes in CBT for Anxiety and

Depression

CBT for anxious youth produced reliable moderate effects

across anxiety, depression, and general functioning out-

comes. A moderate ES of 0.50 suggests that the average

treated child would score better than 69% of the control

group (Weisz et al. 1995), which is consistent with success

rates documented in the treatment literature (e.g., Barrett

et al. 1996; Kendall 1994). The ES calculated for anxiety

outcomes (0.64) was also comparable to previous meta-

analyses. For example, Prins and Ollendick (2003) calcu-

lated mean ESs for anxiety symptoms of 0.99 and 0.49 for

parent- and child-report measures, respectively.

When compared to a waitlist control, CBT produced

effects similar to the overall sample, but when CBT was

compared to an active treatment, CBT appeared to produce

smaller ESs in the small to moderate range. We did not

statistically test for differences in ESs produced by studies

using passive versus active controls because of the small

sample of studies employing active controls. However, a

visual inspection suggests that CBT may produce a smaller

effect for anxiety and general functioning outcomes when

compared against an active control. Further examination is

warranted with a larger sample of studies using active

controls.

CBT for depression demonstrated greater variation

across treatment outcomes. CBT produced moderate

effects for depressive symptoms, near moderate effects for

general functioning, but small effects for anxiety outcomes.

The ES calculated for depression outcomes (0.60) was

smaller than those reported in some previous meta-analyses

(Lewinsohn and Clarke 1999; Reinecke et al. 1998) but

larger than those reported in others (Weisz et al. 2006).

Our study sample was larger than either Lewinsohn and

Clarke (1999) or Reinecke et al. (1998) and we employed

more rigorous statistical controls when calculating effect

sizes. This may have contributed to our smaller ES cal-

culations. Weisz et al. (2006) calculated an ES of 0.34 for

depression measures across all psychotherapy studies and

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an ES of 0.35 for cognitive treatments. We used near

identical statistical analysis as Weisz and colleagues, but

we did not include dissertation studies, nor did we directly

contact authors for missing data.

Depression treatments produced a small ES for anxiety

symptoms (ES = 0.28), which was reliably different from

zero. However, it was also significantly smaller than the

anxiety ES produced by CBT in anxiety studies. A small

ES of 0.20 suggests that the average treated child would

score better than 58% of a control group. This suggests a

statistically reliable relationship but one with potentially

small clinical significance. These effects are consistent

with findings from other meta-analyses in which depres-

sion-focused treatments are associated with significant but

small effects on anxiety symptomatology (e.g., anxiety

symptom ES = 0.39; Weisz et al. 2006).

Process Outcomes in CBT for Anxiety and Depression

Consistent with cognitive-behavioral theory, CBT for

anxious youth produced consistent moderate to large

effects across process variables, with the largest effect

found for behavioral outcomes. The large ES of 1.02

suggests that youth receiving CBT perform better than

about 84% of control participants on behavioral indicators

(Weisz et al. 1995). ES for physiological, cognitive, and

coping outcomes all fell in the moderate range with coping

outcomes approaching a large effect. Upon visual inspec-

tion, the mean behavioral ES appears larger than the

moderate ES values for physiological, cognitive, or coping

outcomes. These results suggest that CBT is particularly

effective in targeting behavioral outcomes. This is certainly

consistent with current theories of anxiety that prioritize

exposure and activation of fear networks in producing

greater approach behaviors (Craske and Mystkowski 2006;

Foa and McNally 1996). Behavioral change would also be

expected given the large proportion of therapy sessions

generally dedicated to exposure exercises. It is common for

anxiety treatments to dedicate at least half of their sessions

to in vivo exposure exercises in which the youth partici-

pates in direct practice in approaching challenging

situations (e.g., Barrett et al. 1996; Beidel et al. 2000;

Kendall 1994; Kendall et al. 1997).

We conducted paired t-tests to directly compare ES

values across process variables within anxiety studies.

These comparisons made use of a smaller sample of studies

because they only included studies in which at least two

process variables were assessed. Here, different trends

emerged. The ES for physiological outcomes (0.54) was

significantly greater than cognitive change (0.20), and a

comparison of coping (0.61) and cognitive change (0.19)

approached significance. Given the results from the overall

sample, we were particularly interested in how behavioral

outcomes compared to others. In 11 studies comparing

behavioral to cognitive change, mean ES for behavioral

outcomes (1.25) appeared larger than cognitive change

(0.74) but they were not statistically different. In the five

studies comparing behavioral (1.10) to coping (1.15) pro-

cesses, no difference was found. It is not clear why these

direct comparisons did not replicate the patterns observed

in the overall sample. It may highlight some methodolog-

ical differences between the studies in the smaller and

larger samples. It may also highlight differences in the

effectiveness of the treatments that comprised the smaller

versus larger sample. It is difficult to make confident

interpretations given the small number of studies that

included assessment of multiple processes. Nevertheless, in

all direct comparisons, cognitive change appeared smaller

than behavioral, coping, or physiological change. Future

investigations might benefit from analyzing differences

between the particular treatment packages that produced

different outcomes.

CBT for depression produced a consistent, but small

effect in cognitive processes. The ES of 0.35 suggests that

64% of treated youth would show greater change than

control participants. This is consistent with cognitive

conceptualizations of CBT that emphasize the importance

of identifying and changing maladaptive thoughts and

beliefs patterns (Beck et al. 1979; Weisz et al. 2003).

Indeed, depression studies assessed a wide range of cog-

nitive constructs including, self-esteem, self-concept,

negative automatic thoughts, and dysfunctional beliefs.

Thus, CBT appears to have a consistent impact in both

specific and general measures of cognition.

Of interest, the mean cognitive ES was close to zero

(0.04) when CBT was compared to active controls. This

appeared significantly smaller than mean cognitive ES

produced by CBT when compared to passive controls

(0.62). Thus, when CBT is compared to other active ther-

apies, often life skills or nonspecific support conditions,

CBT does not lead to greater cognitive change. This raises

the question of treatment specificity for cognitions in CBT.

It is clear that CBT regularly produces cognitive change,

but is cognitive change specific to CBT? The preliminary

evidence here does not support this. There are noted

examples to the contrary in the literature. Kolko et al.

(2000) found CBT did result in significantly less cognitive

distortions when compared to either a behavioral family or

nonspecific support treatment. These conflicting findings

encourage further research and analysis.

Inconsistent with our hypotheses, CBT did not evidence

significant change in behavioral and coping measures. This

was surprising given the importance of behavioral princi-

ples in CB conceptualizations for depression (Clarke et al.

2003; Jacobson et al. 2001). Development of coping skills

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has also been associated with the presence or absence of

depression (Compas et al. 2001). Further, the majority of

reviewed treatments included at least some treatment

modules specifically targeting behavioral patterns (e.g.,

pleasant event scheduling) and teaching coping skills (e.g.,

social, communication, problem-solving skills). The small

sample of studies assessing coping change (n = 2) and the

fact that only one measure was employed (Issues Check-

list) suggest that the calculated value for mean coping ES is

still preliminary. However, behavioral change was assessed

in seven studies employing 10 different measures. These

findings appear more stable.

These results are interesting in light of recent findings

from the adult literature in which a behavioral activation

treatment produced equivalent outcomes to antidepressant

medication and superior outcomes to cognitive therapy in

treating severe depression (Dimidjian et al. 2006). Di-

midjian et al. (2006) did not include analysis of specific

process outcomes, but this dismantling study suggests that

a treatment focused exclusively on behavioral processes

can produce outcomes superior to cognitive interventions

under some circumstances (see also Jacobson et al. 1996).

In contrast, the current results suggest that cognitive vari-

ables are the only processes being activated, or successfully

targeted, during youth treatment. Behavioral processes did

not seem to improve following CBT at all.

One possible interpretation of these results is that CBT

potentially works through different mechanisms in youth

and adults. Cognitive processes may be more central to

change in CBT for child and adolescent populations. This

would be consistent with conclusions made by previous

prevention studies (Allart-van Dam et al. 2003; Munoz

et al. 1995) and by one of our included studies (Kaufman

et al. 2005), which demonstrated that negative automatic

thoughts met criteria as a potential mediator of CBT, but

increased pleasant activities did not. These findings would

be inconsistent, however, with earlier meta-analyses that

suggested cognitive-based therapies were not as effective

with younger versus older children (Durlak et al. 1991).

Alternatively, our results could suggest that youth are

not receiving a sufficient dose of behavioral interventions

to make an impact on behavioral processes. The 16-week,

24-session behavioral activation treatment in Dimidjian

et al. (2006) focused exclusively on behavioral strategies.

In contrast, nearly all of the treatments included here

integrated cognitive and behavioral strategies. It is possible

that treatment developers prioritized cognitive techniques

at the sacrifice of behavioral interventions, or they may

have underestimated the number of sessions necessary to

adequately address behavioral targets. We reviewed our

studies to assess if mean behavioral ES was related to

number of sessions focused on behavioral strategies. Our

preliminary review provided mixed results. Stark et al.

(1987) tested a behavioral problem-solving treatment that

dedicated the majority of its 12 sessions to behavioral

activities and produced the largest mean behavioral ES

(0.39) among depression studies. The second largest mean

behavioral ES (0.30) was found by Rohde et al. (2004) who

implemented the Coping with Depression program

(CWDA). CWDA, an empirically supported treatment for

adolescents, commits at least parts of 12 of its 16 sessions

to behavioral skills, including pleasant activities, social and

communication skills, and problem solving. In contrast, the

lowest mean ES (-0.38) was produced by Vostanis et al.

(1996) who tested a fairly brief integrated CBT program

that dedicated only three out of nine sessions to self-rein-

forcement and social problem-solving. However, the study

that produced the next lowest mean behavioral ES (-0.19)

was Kaufman et al. (2005) who had also employed

CWDA. Thus, dose and treatment differences do not

appear to account entirely for the null behavioral results.

A third possible explanation is that youth-focused

behavioral strategies have not yet been sufficiently

developed to produce significant impact. As a compari-

son, the behavioral activation treatment employed by

Dimidjian et al. (2006) presented treatment within a self-

contained behavioral framework that marks a departure

from traditional reinforcement strategies (Jacobson et al.

2001). Activity scheduling is used as before, but the new

model highlights the centrality of patterns of avoidance

and withdrawal. It places increased focus on functional

assessment, treatment of avoidance behaviors, and

practice in maintaining regularized routines. It also

addresses cognitive rumination as a process rather than

challenging specific cognitive content. As evidence

mounts that behavioral interventions may be more effi-

cacious and possibly easier to disseminate than some

cognitive programs (Dimidjian et al. 2006; Jacobson et

al. 1996), it may be judicious to re-consider how

behavioral principles are put to work in youth-targeted

interventions.

Each interpretation provides avenues for future research,

treatment development, and clinical application. If one

follows the first interpretation, that cognitive processes are

the critical variables to target, then future treatment

development might focus on enhancing cognitive inter-

ventions. Therapy itself might prioritize use of cognitive

strategies to ensure that a youth receives a sufficient dose

of cognitive interventions. Following the latter two inter-

pretations, development and research of behavioral

strategies may represent the domain with greatest growth

potential. Based on the impressive treatment outcomes

documented in the adult literature, enhanced behavioral

strategies might represent the investment with the greatest

potential return. Future direct comparisons (e.g., disman-

tling studies) of cognitive, behavioral, and coping-based

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treatment components will help specify for whom and

through which mechanisms each brand of strategy effects

change. As a caveat, there was little difference between

behavioral and cognitive variables when compared directly

against each other. In the five depression studies that

assessed both cognitive and behavioral processes, no sig-

nificant differences were found between the ESs. The

sample size for this comparison is small, so continued

examination is warranted.

To compare anxiety versus depression studies in their

differential impact on process variables, we used a Q-

statistic analog to analysis of variance. The results

showed significant differences in the degree to which

anxiety and depression studies produced change in

behavioral and coping processes, but not in cognitive

variables. This brand of analysis seems counter-intuitive

since it compares effects produced in distinct samples,

assigned to different treatments. The analog analysis,

however, is specifically designed to compare effect sizes

across mutually exclusive categories (e.g., study) on the

basis of an independent variable (e.g., anxiety vs.

depression; Lipsey and Wilson 2001). The findings here

support the interpretation that meaningful differences

exist in how CBT impacts youth across anxious and

depressed samples. In the case of behavioral processes,

the results could reflect the interpretations offered earlier.

Anxiety treatments may commit greater proportion of

treatment to exposure-based strategies and/or the appli-

cation of behavioral strategies may be more fully

developed in anxiety treatments.

A second possibility is that these results support the

existence of actual mechanistic differences in CBT for

anxious and depressed youth. Although CBT was equally

effective in producing primary symptom change in both

anxiety and depression studies, CBT produced compara-

tively greater behavioral and coping change in anxiety

samples. Although far from definitive, the results support

further research to determine if CBT operates through

varying mediational pathways in anxious and depressed

youth. Over time, such findings may have implications for

many domains of clinical research. For example, the field is

currently reconsidering the basis under which disorders are

classified within DSM-V (Krueger et al. 2005). Conceptual

and taxonometric models are being considered (Brown and

Barlow 2005; Watson 2005). The results from the current

review suggest that how individuals respond to treatment

may be another criterion used to classify disorders. To the

extent that common change mechanisms are identified,

disorders may be closely linked. To the extent that different

mechanisms are evident, classification into separate groups

may be supported. The results here support the possibility

that different processes may mediate CBT for anxious and

depressed youth.

Disentangling Mechanism from Outcome

In truth, mediational pathways are more complex than we

can present here. Multiple pathways (e.g., multi-causality,

reciprocal causality, bi-directional changes) tend to be the

rule rather than the exception (Kazdin and Nock 2003).

Behavioral interventions may work through behavioral

processes, cognitive mediators, or both. For example,

behavioral activation may increase a youth’s contact with

natural reinforcers (thus increasing the likelihood of future

behavior) or it may provide the opportunity to disconfirm

negative beliefs about the situation. Sequence of change

and suppression effects may also complicate matters. To

continue our example, initial contact with natural rein-

forcers may be necessary to achieve cognitive change (e.g.,

increased self-efficacy). However, if the latter cognitive

change is more salient to the youth, or if the youth ascribes

more explanatory power to cognitive processes, the role of

the initial behavioral change may be difficult to detect if

assessed exclusively at posttreatment.

In the current archival review, which relied on published

data of posttreatment assessments, it is impossible to dis-

entangle the magnitude and sequence of change in such

complex pathways. Indeed, two of our included studies

(Fine et al. 1991; Stark et al. 1987) identified delayed

effects for candidate mediators. In Fine et al. (1991)

Therapeutic Support produced superior posttreatment

scores on a measure of self-concept compared to Social

Skills Training. However, by 9-month follow-up, both

treatments demonstrated comparable effects. Stark et al.

(1987) found no differences between a Behavioral Problem

Solving and a Self Control treatment at post-treatment on

measures of social withdrawal. By 8-week follow-up,

Behavioral Problem Solving achieved superior effects in

reducing withdrawal. These sleeper effects emphasize the

need for continuous assessment throughout and following

treatment, and remind investigators to think broadly about

the timeframe selected for analysis.

In the end, our findings provide evidence partially

consistent with Weersing and Weisz’s (2002) Intervention-

Specificity Test. On average, CBT produced consistent

change in theory-specific variables for anxious samples and

was associated with cognitive change in depressed sam-

ples. As discussed earlier, narrowing the field of possible

mediators is worthwhile as a first step to identifying

mechanisms (Kraemer et al. 2002). The same can be said

for documenting that theory-specific change occurs as we

expect. Process variables shown to have consistent rela-

tions with CBT should be assessed systematically in

comparative clinical trials comparing CBT with other

therapies. Demonstration that the process is reliably and

specifically related to CBT would elevate the variable’s

standing as a potential mediator of CBT. To determine if

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the variable formerly mediates the effects of CBT, one

would have to demonstrate that the mediator meets the

established criteria for mediation (Baron and Kenny 1986;

MacKinnon et al. 2002). To establish the mediator as a

mechanism, a subsequent RCT could be conducted in

which a treatment enhanced with those components asso-

ciated with the mediator can be tested against the original

treatment. Demonstration that the enhanced treatment is

more effective than the original treatment would establish

the mediator as a mechanism (Kraemer et al. 2002). In

sum, the current review helps identify potential mediators

but several further steps are required to demonstrate formal

mediation or to establish any causal relationships associ-

ated between mechanisms and outcomes.

Limitations

There are several limitations to the current review. As in

any meta-analysis, the results are limited to the studies

included in analyses. Our inclusion criteria were focused

and included only treatments rigorously tested in an RCT

that assessed both process and outcome. These strict cri-

teria eliminated several prominent RCTs from both the

depression (e.g., TADS 2004; Weisz et al. 1997) and

anxiety literatures (e.g., Bernstein et al. 2005; Nauta et al.

2003). These RCTs represent important and methodologi-

cally rigorous studies. Had these trials assessed and

reported process outcomes, we may have observed differ-

ent outcomes in our own analyses.

Further, analysis of process and outcome variables was

limited to assessments conducted in the original trials. This

presented several limitations. First, very few studies

assessed process and outcome at multiple time points. This

limits any detailed analysis of time course, an important

factor in demonstrating a sequential relationship between

mediator and outcome. Second, many but not all studies

used distinct measures to assess process and outcome. For

example, the RCMAS and STAIC were common indicators

of treatment outcome, and our analyses used subscales of

these measures to represent cognitive and physiological

processes. This leads to potential confounds on both con-

ceptual and methodological grounds. Analyses in the

current report were not affected by this overlap because

mediator and outcome measures were never correlated or

compared directly. Comparisons were either across various

process variables or across different types of outcome;

thus, issues of shared variance and multicollinearity were

avoided. When interpreting results, the reader should be

cautious in directly comparing process and outcome effect

sizes, because changes in subscales (process variables)

would likely be correlated with changes in total scores

(outcome variables). Future analyses that make direct

comparisons should consider this overlap, and prospective

clinical trials should aim to measure process and outcome

using conceptually distinct and methodologically diverse

approaches (e.g., multi-method, multi-source) to facilitate

mediation analysis.

Our target comparison was CBT versus passive or active

controls. We did not compare CBT to other theoretical

approaches, such as to Interpersonal Therapy, even though

one trial was available to do so (e.g., Rossello and Bernal

1999). We also did not compare different forms of CBT,

such as individual versus family or group CBT. There were

several studies that included multiple forms of CBT, but

the number of studies is still too small to make meaningful

use of meta-analytic procedures.

We pooled ES values up to the level of treatment rather

than to individual studies. There are potential risks to this

approach in that multiple CBT conditions studied within a

single study are more likely to be similar than CBT treat-

ments across studies. There is precedence for this approach

(e.g., Weisz et al. 2006) in which it was acceptable to pool

ES values up to the most conservative level appropriate to

each test, based on the conceptual goals of the analysis.

Weisz et al. (2006) did not collapse ES values across

treatment groups. In the current review, the principal

interest was establishing the effect of an average CBT

protocol on specific targets when compared to a control

condition.

We also did not conduct separate analyses for parent

from child reported measures. Previous meta-analyses have

identified some significant differences in mean ES for

parent and child reported outcomes (e.g., Prins and Ol-

lendick 2003). Given the often divergent perspectives of

child and parent reporters, this approach should be pursued

in future meta-analyses. The goal here was to provide an

overview of the overall effects of CBT.

Our analysis may also be susceptible to what Smith et

al. (1980) described as measure reactivity. Measures that

conceptually mirror the nature of the treatment they are

evaluating may yield higher effect sizes. We exclusively

included process variables considered conceptually

important to CBT. Future meta-analyses could include

specific and nonspecific (e.g., alliance, engagement) tar-

gets, as well as processes from contrasting theoretical

approaches (e.g., intrapsychic insight). This approach may

provide a fuller picture of the specific and nonspecific

effects of CBT and other therapies.

Conclusion

Limitations notwithstanding, the current study provides the

most comprehensive review to date of specific effects of

CBT for anxious and depressed youth. It also provides

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evidence for potentially differentiating mechanisms in the

treatment of anxiety and depression. Alternately, it pro-

vides areas for research and development in treatment.

Results from the anxiety literature document significant

support for several theory-specific process variables.

Anxiety researchers may now pursue mediator and mech-

anism research confident that multiple behavioral and

psychological processes make good candidates for exami-

nation. Results from the depression literature suggest that

additional groundwork may be wise. Although CBT

appears to achieve consistent significant effects on

depression outcomes, there are few consistent candidate

variables to explain how effects are mediated. Cognitive

processes currently receive the most support, but lessons

from the adult literature remind us of the great potential in

behavioral treatments and related mechanisms. Meaningful

work remains to be done to develop effective behavioral

treatments and to establish reliable and valid methods for

assessing behavioral change.

Acknowledgment The authors thank Kelly Pugh and Jessica Dahan

for their tireless efforts and organization in tracking down the many

journal articles that informed study analyses.

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