the psychological science of addiction

The psychological science of addiction

Elizabeth Gifford & Keith HumphreysVeterans Affairs and Stanford University Medical Centers, Palo Alto, CA, USA

ABSTRACT

Aim To discuss the contributions and future course of the psychological science of addiction. Background Thepsychology of addiction includes a tremendous range of scientific activity, from the basic experimental laboratorythrough increasingly broad relational contexts, including patient–practitioner interactions, families, social networks,institutional settings, economics and culture. Some of the contributions discussed here include applications of behav-ioral principles, cognitive and behavioral neuroscience and the development and evaluation of addiction treatment.Psychology has at times been guilty of proliferating theories with relatively little pruning, and of overemphasizingintrapersonal explanations for human behavior. However, at its best, defined as the science of the individual in context,psychology is an integrated discipline using diverse methods well-suited to capture the multi-dimensional nature ofaddictive behavior. Conclusions Psychology has a unique ability to integrate basic experimental and applied clinicalscience and to apply the knowledge gained from multiple levels of analysis to the pragmatic goal of reducing theprevalence of addiction.

Keywords Addiction, behavior, psychology, substance use disorder intervention.

Correspondence to: Elizabeth Gifford, Program Evaluation and Resource Center (152-MPD), 795 Willow Road, Menlo Park, CA 94025, USA.E-mail: [email protected] 7 July 2006; initial review completed 20 September 2006; final version accepted 16 October 2006

INTRODUCTION

Psychology is the study of the individual in context, andas such is fundamental to the clinical and research aspi-rations of the addiction field. ‘Addiction’ is a hypothesis,namely that a cluster of correlated phenomena are linkedby an underlying process (or as Gertrude Stein mighthave put it, that there ‘really is a there, there’). Withoutthe behavior of persistent, destructive substance use, theenvironmental availability of the substance itself, and theenvironmental effects on the behavior, it would be diffi-cult from a scientific viewpoint (and meaningless from aclinical viewpoint) to verify the hypothesis that addictionreally exists. This does not limit addiction to observablebehaviors but does identify behavior–environment inter-action as the central concern.

Throughout this paper we argue for attending to thedynamic multi-dimensional adaptations involved inperson–environment interactions. We describe severaldomains in which psychology, as a focused and flexiblescience, is making contributions to understanding thedevelopment, maintenance and recovery from addiction.From this knowledge base we derive some principles

defined in the traditional sense as a ‘a rule or law con-cerning the functioning of natural phenomena [emphasisadded]’ [1]. We emphasize how a functional approachprovides a useful means of orienting scientific efforts,integrating basic and applied domains and leading trans-disciplinary or interdisciplinary research efforts. We closeby illustrating how the functional principles derived fromthis knowledge base contribute to a progressive, incre-mental science of addiction.

Before proceeding to our review of psychology’s sub-stantive and conceptual contributions to the field, wewould acknowledge all too briefly psychology’s far-reaching contributions to methods. Graduate psychologytraining programs typically place substantial emphasison measure development and assessment. One dividendfrom this investment is many widely used instrumentsdesigned by psychologists to assess individuals, families,treatment programs and environments; for example,Moos’ coping responses inventory [2] and social ecologyscales [3], Halstead & Reitan’s neuropsychological testbattery [4] and McLellan and colleagues’ [5] AddictionSeverity Index. Psychologists have also been leaders inthe development and application of quantitative

ADDICTION AND ITS SCIENCES doi:10.1111/j.1360-0443.2006.01706.x

© 2007 Society for the Study of Addiction. No claim to original US government works Addiction, 102, 352–361

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methods, including accounting for regression to themean [6], establishing construct validation [7,8] andimproving quasi-experimental and experimental treat-ment evaluations using mediational modeling [9] andmeta-analysis [10]. Indeed, experimental studies withhuman participants in addiction are almost entirely theprovince of psychologists, including but not limited tomany of the methods used to evaluate learning. All thesemethodological contributions made possible theadvances on which we focus in this essay, as well as innu-merable advances that space limitations will prevent usfrom discussing here.

ADDICTION AND MOTIVATION

The best scientific evidence for addiction is providedby persistent substance use in the face of cumulativecosts, such as psychological distress, social conflictand physical harm to health.

Addiction is not simply a physiological process, but theaction of multi-dimensional individuals behaving in aparticular fashion in certain contexts. Although manyprofessional and lay individuals speak of addiction as ifit were synonymous with tolerance and withdrawal,both of these phenomena can occur without addictivebehavior [11]. Indeed, even if we developed a blood testthat could measure precisely the degree of an individu-al’s physical tolerance to a drug, it would be hard toconvince ourselves or that person that they wereaddicted without the evidence of drug-seeking andusing, i.e. a particular behavior–environment interac-tion. In addition to making psychology of central rel-evance to understanding addiction, this distinction alsoaids in the interpretation of research findings. It mayexplain, for example, why an episode of sustained absti-nence in out-patient treatment predicts subsequentabstinence when detoxification alone does not. Thechange in the persistent behavior, not the absence of thechemical alone, improves the likelihood of future absti-nence [12].

Descriptions of addiction often use terms such as‘overwhelming desire’ or ‘out of control’ to describe thepersistence of substance use in the face of damaging con-sequences [13]. Yet behavior that looks ‘out of control’ tothe observer is in fact an individual’s response to theirenvironment and perceived options at the time. Models ofmotivation attempt to characterize the processes under-lying these seemingly irrational choices. These modelsposit a range of motivations. Stated generally, people usedrugs because drugs feel good (positive reinforcement[14], because drugs reduce or remove the experience offeeling bad (negative reinforcement [15]), because brainprocesses enhance the reward value of substances overtime to the point that automatic addictive behaviors

occur without thinking (a combination of the effects ofdrugs on the brain’s reward systems, particularly dopam-ine signaling in the nucleus accumbens, respondent con-ditioning and incentive sensitization [16–18]) andbecause of other cognitive processes (e.g. expectancies,beliefs, mental representations, self-efficacy and coping[19]. More recent models synthesize these variousdynamic motivations [13,20]). Notably, all the abovemodels are concerned with understanding how and whyaddicted individuals persistently respond to certainimmediate rewards [13].

SOCIAL CONTEXT

Addictive behavior occurs within a social context,which can serve as a risk or protective factor. Socialcontexts and individuals influence one another.

What are the contexts that influence the above-described motivations? Psychology has led the field inidentifying the importance of social connection inaddiction, including the conceptualization and measure-ment of the social ecology in which addicted peoplereceive care and in which they live [21,22]. Socialcontext serves as both a risk factor and protective factorfor substance use, playing an important role in addic-tion’s initiation, escalation, maintenance and relapse;and conversely in its prevention, treatment and long-term resolution. Relevant social contexts include thefamily, provider–patient relationships, treatment envi-ronment, peer groups and friendship networks, worksettings, self-help organizations, neighborhoods and cul-tural groups, including religious/spiritual communities.As just a few examples, research in which psychologistshave been involved has shown that association withsubstance-using peers is a major risk factor for initia-tion, escalation and relapse [23]; that the quality ofprovider–patient relationships contributes to patientretention in substance use disorder treatment [24]; thatparticipation in a 12-Step community after treatmentfacilitates ongoing recovery [25]; that improving paren-tal functioning and resources improves substance abuseoutcomes for adolescents [26]; and that participation inorganized religion and the family and social contextsthat promote such participation are among the stron-gest predictors of not initiating substance use in chil-dren and adolescents [27]. Clearly, the dynamicinterface between the social group and the individualhas a powerful influence on addiction.

Several general psychological theories describe therelationships between social context and individualaddictive behavior. Among these, social control theoryemphasizes the motivational effects of the bonds betweengroup members, social learning theory emphasizes theimportance of role models in the development of

Psychology of addiction 353


substance-related behaviors and attitudes, and stress andcoping theory emphasizes the impact of stressors result-ing from social disorganization on the coping resources ofthe individual [28]. All these approaches describe influ-ence processes moving bidirectionally between individu-als and their social setting [21]. Current psychologicalresearch is focused on characterizing these mutualinfluence processes; for example, some of the dynamicadaptational interactions between environments andindividuals described below.

FUNCTIONALBEHAVIORISM/BEHAVIORALECONOMICS

Addictive behavior interacts dynamically andlawfully with its environment.

The basic principles of learning and conditioningobserved by Thorndike [29] and other psychologists (i.e.operant and respondent paradigms) continue to provide aframework for understanding the interactions betweenenvironment and addictive behavior. For example, Herrn-stein’s Matching Law characterizes patterns of interac-tion between changes in reinforcement opportunities andindividual choice [30]. The Matching Law showed thatthe ratio of behavior distributed between two choices will‘match’ the ratio of reinforcement distributed acrossthem, expanding the notion of functional relationships toinclude a broader environmental context rather than justa unitary reinforcer. For example, environments withgreater levels of available positive reinforcement ingeneral may make it less likely that a particular positivelyreinforced behavior, such as substance use, will occur[31]. The Matching Law has provided the basis for manybehavioral economic theories of choice which attempt toquantify the relationships between benefit/cost ratios ofsubstance consumption and benefit/cost ratios of otheractivities [32].

We would note here that ‘reinforcement’ is a fre-quently misunderstood term that refers to a fundamen-tally personal phenomenon. The form or topographicfeatures of an event do not define it as a reinforcer (e.g.giving a weeping client candy is unlikely to reinforcecontinuing discussion of the costs of using); rather,reinforcement refers to the functional impact of theexperienced event for that particular person (moretechnically, whether the event functions to increasethe probability of the behavior it follows in a specificcontext [33,34]). Reinforcement is a function of amulti-dimensional person interacting with a complexenvironment. Attention, perception and motivation, forexample, may be critical in establishing how a reinforcerfunctions in any given setting.

Learning principles characterize certain dynamicinteractions between individuals and their environments,and also offer a unique bridge for integrating basic andapplied domains. The most successful psychosocial treat-ments for addiction have applied basic functional modelsto clinical settings [35]. Contingency management, forexample, an empirically supported treatment for stimu-lant abuse and for promoting retention in methadonemaintenance programs, applies operant processes ofcontingent reinforcement such as vouchers for cleanurine tests and take-home doses for attending cliniccounseling sessions [36]. Motivational interviewing, anempirically supported cognitive behavioral treatment forsubstance abuse, positively reinforces treatment relevantbehaviors such as ‘change talk’ using interpersonal pro-cesses within the therapy session (i.e. support, empathyand contingent feedback; [37,38]).

Dynamic functional processes of problem resolutionmay also occur outside treatment settings [39]. The con-tingency of reinforcement mediates contingency man-agement treatment, as specified in its functional model.Yet treatment is only one structured context where theseprinciples operate. Other social contexts such as 12-Stepfellowships or religious communities may also reduce thelikelihood of drinking or relapse by naturally reinforcingadaptive alternatives to substance use, e.g. sponsors in12-Step programs may provide social support contingenton abstinence and encourage socially normative activi-ties such as working, self-care, family life, recreationalactivities, etc. [40]. Communities bring these functionalprocesses into play without the conceptual framework ofbehavioral psychology, e.g. ‘reinforcement’, etc. [41].

THE PSYCHOLOGICALLY INFORMEDNEUROSCIENCE OF ADDICTION

Addiction involves learned responses to a drug andto the environments in which drug taking isexperienced. The brain encodes these learninghistories as neuroplastic adaptations includingalterations in the mesolimbic dopaminereinforcement systems.

Learning principles link not only basic and applieddomains within psychology but also psychology andother disciplines, thus offering one natural point of inter-disciplinary integration. Psychological data derived fromthe application of learning principles in animal modelshave been essential to progress in the neurobiology ofaddiction. As stated recently in this journal, the agenda ofmodern addiction brain science is to validate molecularand neurochemical candidate systems functionally bydemonstrating their causal relationships with addictiveprocesses [42]. Basic behavioral methods provide aframework for evaluating the function of candidate

354 Elizabeth Gifford & Keith Humphreys


neurobiological systems (e.g. place preference paradigms,drug self-administration, reinstatement of drug seeking,etc.). Relevant systems include those involved in the neu-ropharmacological processes of behavioral response tosubstances as well as the neuroadaptive mechanismswithin specific neurocircuits that may mediate addictivebehavior, such as the circuits recruited in the transitionfrom occasional use to uncontrolled use, from positivelyreinforced to negatively reinforced addictive behavior, orfrom compulsive use back to controlled use or abstinence.Studies of mesolimbic dopamine circuits, for example,have identified neuroadaptive processes linked to rein-forcement in general (e.g. [43]) and have also identifiedeffects specific to drugs of abuse that may lead to theovervaluation of drug rewards as compared to naturalreinforcers [44,45].

Cue-elicited craving offers one example of psycholo-gy’s leadership role in transdisciplinary neuroscience col-laborations [46]. The presence of cues associated with theavailability of learned reinforcers such as alcohol or otherdrugs will increase behavioral responding for theserewards [47]. Cue conditioning is a key element in thedevelopment and maintenance of addiction, and cue-elicited craving a key aspect of relapse [48]. The neu-ropeptide cortisol-releasing factor (CRF) offers onepossible pathway for the relationship between stress, cueconditioning and relapse in habitual users [49]. CRFreleased in the nucleus accumbens shell in response tostress may increase the incentive salience of cues signal-ing the availability of learned reinforcers, increasingbehavioral responding for rewards when such cues arepresent. Because drug withdrawal can be a significantstressor, potently releasing CRF in limbic brain circuits,this process may become a negative reinforcement cycledriving ongoing drug use, described as ‘the downwardspiral of addiction’ [50]. Notably, this explanationdescribes neurobiological mechanisms conceptualized interms of behavioral principles of negative reinforcement.

Cue-elicited craving has been associated with neu-ronal processing in the anterior cingulate cortex andfrontal cortex [51–53]. A related promising line of neu-roscience research examines how the frontal cortexinhibits automatic responding in immediate decision-making tasks. Performance on executive function/task-switching tests (which include inhibition) has beenassociated with neural processing in the prefrontal cortexin both neuroimaging and electrophysiological studies[54–56]. For example, several studies have demonstratedthat activity in areas of the frontal cortex is associatedwith the ability to alter responding in a well-trainedsignaled response task [57,58]. These studies are provid-ing important information on individual decisions aboutbehavior choice, and about how alternate behaviors canbe produced even when a given response has become

‘automatic’ and favored. Understanding this process hasobvious importance for modifying impulsive behavior inaddiction. In particular, these studies have shown thatthe ability to inhibit automatic responding by the frontalcortex is easily overwhelmed by loading of workingmemory, which occurs when experiencing stressors suchas cravings. In other words, a person may not be able tostop a well-trained behavior such as drug taking usingfrontal cortex inhibition when they are experiencing highlevels of cue-elicited craving.

Psychology has thus expanded, and at times tran-scended, its own discipline, applying learning principlesand other contributions toward improving our under-standing of the neuroanatomical substrates of affectiveand cognitive processes such as stress and executive func-tion. The field continues to play a pivotal role in identify-ing the dynamic neurobiological processes involved invulnerability to addiction, consequences of substance useand important aspects of addiction including relapse, lossof control, craving and drug choice.

Psychology can also serve as a useful guard againstconcluding that because brain systems are involved inaddiction, all solutions to addiction are found in the brain(or in genes; see [59]). The environmental stressors thatfacilitate certain genetic expressions are not equal in theireffects across individuals. Psychological factors influencehow stressors are appraised and coping responses canminimize or augment their impact; and changes in theenvironment can change individual behavior. The behav-ior economic literature, for example, suggests the impor-tance of restricting access to substances as a strategy forreducing addiction, as it raises the behavioral costs of useand thereby increases the attractiveness of other behav-iors. This has been well demonstrated in the effect of ciga-rette cost on smoking [60].

INTERVENTION

Many empirically based substance use disorderbehavioral interventions facilitate recovery fromaddiction, although not necessarily for the reasonsspecified in their theories.

Research indicates that well-specified psychosocial sub-stance use disorder treatments have a positive impact onoutcome, and there are many such treatments fromwhich to choose. The US National Institute of DrugAbuse, the British Association of Psychopharmacology[61] and the Swedish Council of Health Care TechnologyAssessment [62] are among notable organizations whohave compiled lists of empirically supported treatmentsfor addiction and its prevalent comorbidities. Most ofthese treatments were developed by psychologists basedon psychological theories, including motivational



interviewing, social skills training, combined behavioraland nicotine replacement therapy for nicotine addiction,structured family and couples therapy and communityreinforcement approach and family training [63].

Psychologists have taken a leading role in proposingnew theories of treatment and in promoting rigoroustreatment evaluation, including the development oftreatment integrity measures and other methodologicalinnovations (e.g. despite occasionally being portrayed asa ‘touchy-feely’ irrationalist, the psychologist Carl Rogershelped begin the tradition of rigorous evaluation of psy-chotherapies; see [64]). The results of trials comparingwell-specified behavioral therapies (and at times behav-ioral versus pharmacotherapies) show that different well-specified substance use disorder treatments usually havesimilar levels of efficacy [65–67]. However, exceptions tothis rule exist. For example, a recent meta-analysis ofcue–exposure therapy [68] yielded equivocal evidence forits efficacy and also failed to support its specified mediat-ing model, i.e. reductions in cue–reactivity are not pro-duced by this treatment and/or do not effect the criticalbehaviors [69].

Large controlled trials including mediational analyseshave rarely identified a treatment with reasonable evi-dence for its purported mechanism of change. Amongthe few exceptions appear to be contingent reinforcementof abstinence in cocaine addiction [70] and AlcoholicsAnonymous participation in 12-Step facilitation counsel-ing [71,72]. Accurately identifying mediators is vitallyimportant, because clarifying the critical aspects of treat-ment may allow us to improve its potency and determinefor whom a particular treatment might work [73]. It isnot as useful to know, for example, that men do better incertain smoking cessation treatments than womenunless we also know why and what to do about it (see [74]for an excellent discussion).

WEAKNESSES

Psychology has made major contributions to under-standing addiction, but we would be the first to acknowl-edge that it has also occasionally ‘filled a much-neededgap’ in the field’s approach and knowledge. Psychologistshave at times tried to explain individual behavior withoutsufficient appreciation of context. US psychology hasbeen the worst offender, in some ways reflecting the largercultural narrative that individuals create their own livesand triumph over all contexts (or if they do not, they haveonly themselves to blame). For example, for every pub-lished article concerning ‘drug use and poverty’ in thepsychological literature, more than 50 articles focus on‘drug use and personality’ [75]. Callous behavior by soci-eties and governments are justified too easily when prob-lems shaped by powerful environmental forces are

attributed entirely to intrapersonal variables. Disregardfor context has led to some psychologists making pro-nouncements on the ‘universal features of addiction’(among many other features of human existence) on thebasis of how small samples of white, middle-class under-graduates have filled out a questionnaire.

Psychologist have also at times over-psychologized‘addiction’ by not taking drugs sufficiently seriously asenvironmental features with unique, genuine and power-ful properties not determined solely by the individualuser’s expectancies, psychodynamic conflicts or cognitivebiases. Psychologists who market services for alleged‘addictions’ to work, shopping and television shouldweigh carefully the public health implications of implic-itly equating long days at the office, discounts at Sains-bury’s and re-runs of Star Trek episodes with nicotine,heroin and alcohol. The latter three environmental fea-tures should be handled differently by programs andpolicy makers because they are objectively different thanthe former three, no matter how many people say thatthey feel addicted to them, ‘just like being addicted todrugs’. The inner life of individuals is, of course, animportant part of psychology, but only in the context ofenvironmental features interacting with behavioralresponses, and what the individual learns from thoseinteractions. Acontextual theories risk addressing only asmall portion of an integrated system, and thus misdirectour attention to less relevant details at the expense offactors related more directly to the phenomenon ofaddiction [13].

SETTING THE COURSE: TREATMENTRESEARCH AS AN EXEMPLAR

What can psychology do in the future to avoid repeatingmissteps and to break into new directions? Clarifying ourtheoretical assumptions may help to guide futureresearch efforts. The field of treatment research offers oneexample.

Decades of research on clinical treatment has led to asubstantial knowledge base. We know that treatmentbenefits a significant proportion of addicted people, andwe have a variety of reasonably effective treatments tooffer. However, the results of large, well-funded and well-designed treatment research studies such as ProjectMATCH [76], the UK Alcohol Treatment Trial [77] or theVA Multisite Substance Abuse Treatment Study [78]show that null findings are arguably the single mostcommon outcome in large-scale substance use disordertreatment studies. Although one cannot prove the nullhypothesis that treatments do not differ, the consistencyof these non-results in well-powered studies suggests thatour theories are failing to capture critical factors. It istime to consider additional strategies.



Psychologists have long discussed factors common todifferent treatment approaches that may be responsiblefor treatment effects. The therapeutic relationship is themost frequently researched of these so-called ‘commonfactors’ [79]. Although researchers described originallythe therapeutic relationship as ‘non-specific’ in ananalogy to the pharmacologically inert component ofmedication, it has become clear that the therapeutic rela-tionship is an active interaction [80,81] that mayincrease treatment engagement and other recovery-relevant behaviors [24,82]. Currently, the critical ques-tion is how the therapeutic relationship functions, i.e.how does the provider interact with the patient in specificprocesses which change the patient’s behavior and areresponsible for treatments’ effects [83]?

Miller [84] recently distinguished ‘name brand’ treat-ments from the mediating processes by which treatmentsexert their effects. Summarizing the current knowledgebase on addiction in the biological, psychological, socialand intervention research domains, Miller and colleaguesdrew a number of evidence-based conclusions: addictivebehavior is reinforcing, chosen behavior; emerges gradu-ally and occurs along a continuum; does not occur inisolation but as part of behavior clusters; occurs within afamily context; responds to changes in reinforcement; isaffected by a larger social context; has identifiable risk andprotective factors, tends to become self-perpetuating onceestablished; is motivated behavior; and is influenced bythe therapeutic relationship [84]. Notably, all these con-clusions reflect a functional perspective.

Psychology has an opportunity to lead the addictionfield by identifying functional concepts that characterizethe multi-dimensional processes responsible for treat-ments’ effects. Clarity about these processes will permitsystematic treatment improvement [35,83]. Conductingtransdisciplinary research requires a shared conceptualor theoretical framework that integrates knowledge fullyacross disciplines [85–87]. Among the many contribu-tions discussed previously, psychology has also developedthe most precise scientific methodology for validatingconceptual constructs (e.g. multi-trait–multi-methodmatrices); such methods might be used to identify theo-retically based functional processes that synthesizeresearch across disciplines [88].

Functional models, by definition, characterizeindividual–environment interactions, and thereforeprovide a pragmatic means of changing behavior viaenvironmental factors. For one example, behaviorchange is more likely with abstinent supportive socialreinforcement [28]. In applied settings, treatment per-sonnel who behave in a supportive rather than a confron-tational manner appear to improve the likelihood ofpositive outcomes [82], perhaps by increasing patientinvolvement [89] and helping patients learn to accept

and respond differently to internal states previously asso-ciated with using [90]. In a recent study, patients fromtreatment programs with supportive, involved relation-ships were more likely to respond adaptively to internalstates associated previously with substance use, developconstructive social relationships and achieve long-termtreatment benefits. This functional model accounted for41% of the variance in outcomes 2 years after treatment[41]. Researchers continue to examine the processesinvolved in socially reinforcing interactions via socialneuroscience, basic and clinical process and outcomeresearch.

Emphasis on function provides a common empiricalground for examining the behavior change processacross treatment modalities. The pre-existing practices ofa variety of treatments and treatment settings includefactors related to positive outcomes [41]. Identifyingthese practices might bring parsimony to the multiplicityof available treatments and aid in dissemination by build-ing on aspects of treatment that providers already deliver.The dissemination gap between empirically supportedtreatments and substance use disorder treatment pro-vider practice is arguably a result of the failure ofresearchers and administrators to address the functionalaspects of clinicians’ behavior. Rather than simplyattempting to impose top-down change, viewed from afunctional perspective the dissemination questionbecomes: ‘How do we facilitate behavior change in thetreatment provider?’. To answer this question one firstneeds to understand what providers are doing and thenuse this information to shape changes in behavior, i.e.build upon constructive evidence-based practices andweaken competing alternatives. Data regarding the func-tional dimensions of clinician behavior include studiesshowing that meaningful changes in treatment provisionare less likely with a single workshop (e.g. [91]) than withongoing supervisory feedback [92]. Functional principlesoffer specific environmentally based ways of facilitatingbehavior change in both patients and providers, includ-ing building on current repertoires, shaping new ways ofinteracting and providing systematic methods for gener-alizing behavioral changes [93].

In short, using a functional approach to modelingbehavior change directly targets the patient behaviorsthat lead to better long-term outcomes; serves as a pointof integration for interdisciplinary research efforts aimedat characterizing the process of behavior change; pro-vides pragmatic methods for influencing these changes inbehavior; and builds upon what programs and providersare already doing in order to improve treatment delivery.

A final compelling reason for focusing scientific effortson processes of change is that these adaptational or func-tional principles apply beyond the treatment context. Theprocesses that contribute to improvement in treatment



may also be implicated in recovery in mutual helporganizations, processes involved in ‘natural’ recovery(which, indeed, is how most individuals overcome addic-tion), prevention and recovery in religious/spiritual cul-tural communities, etc. From a functional perspective,treatment essentially provides a structured environmentwithin which to influence (i.e. boost variability in) rel-evant processes. Thus treatment is particularly importantfor those who do not have access to these types of contextin their natural environment or who are in need of moreintense exposure to curative environments. Broadeningthe lens to include context also entails recognizing thattreatment may be simply one chain in a larger causalmodel [94]. Clients describe their own change process inboth intrapersonal and interpersonal terms, embedded inthe contexts within and outside the treatment setting[95]. Indeed, causal mediators of treatment may be diffi-cult to find because the critical processes occur outsidetreatment. For example, Longabaugh and colleagues [96]found that improvement in social skills did lead toimproved alcohol treatment outcomes, as described bytheir theoretical model, but causal chain analysesrevealed that these changes in social functioning did notoccur within treatment.

Most members of the field concede that addictionresearch is more informative when it is theoreticallybased. Less commonly discussed is the fact that ourassumptions specify what sort of theoretical explanationsare considered adequate and thereby guide the directionof inquiry. In general, the field of psychology has sufferedfrom a proliferation of theories with relatively littlepruning [35] (see [13] for an excellent discussion; also[97]). However, the propagation of labels should not bemistaken for scientific progress [98]. Psychology’s com-mitment to rigorous evaluation offers both great progressand humility. We may need to surrender some of ourcherished ways of speaking in order to further ourongoing goal of improving interventions that treat andprevent addiction.

CONCLUSION

We have adumbrated psychology’s contributions toaddiction in the social, behavioral, neurobiological andintervention domains. This survey fails to describe innu-merable contributions, including much of cognitivepsychology, developmental psychology, physiological psy-chology and neuropsychological assessment. Further,our assumptions and the principles we derive from thesedomains are our own, and both other assumptions andother interpretations are possible. We simply hope toshow the relationship between definitional assumptions,explanations and progress in what we view as a particu-larly important and vital knowledge base.

The psychologically derived principles or descriptionsof the ‘functioning of natural phenomena’ presentedhere share an assumption, namely that addictionresearch is concerned fundamentally with interactionsbetween individuals and their environments, and thatmaintaining clarity about our subject matter will helppromote a focused, flexible and progressive addictionscience. Future questions include application of theseprinciples to broader social contexts. For example, howmight we apply these principles to addiction in the publichealth and public policy domains [99]?

Addiction involves dynamic adaptations occurring atmultiple levels that are influenced by a variety of contextsincluding but not limited to treatment environments. Ifwe want to improve our understanding of addiction andrecovery, we should examine these processes directly. Psy-chological science is well suited for this endeavor.

Acknowledgements

This work was supported by the US Department of Veter-ans Affairs Office of Mental Health Services and HealthServices Research and Development Service. We thankStephen Maisto, Rudolf Moos and Robert West forextremely helpful comments and discussions.

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