schizotypal personality in mature adults

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Personality and Individual Differences 40 (2006) 77–85

Schizotypal personality in mature adults

Johanna C. Badcock *, Milan Dragovic

School of Psychiatry and Clinical Neurosciences, University of Western Australia, Perth,

Centre for Clinical Research in Neuropsychiatry, John XXIII Avenue, Mt. Claremont,

Perth WA 6010, Australia

Received 18 October 2004; accepted 16 June 2005Available online 22 August 2005

Abstract

The goal of the present study was to examine the influence of age and gender on the factor structure ofthe Schizotypal Personality Questionnaire (Raine, 1991). Schizotypal traits were assessed in a random sam-ple of mature, adult community volunteers (average age 40 years). Four competing models of the latentfactor structure were tested in the full sample (N = 352). The resulting three-factor model was then assessedseparately in males and females and in stratified subsamples, reflecting three age cohorts. The resultsshowed that, in mature adults, males had higher scores than females on No Close Friends and ConstrictedAffect whilst females had higher scores on Social Anxiety and Odd Beliefs subscales. Older adults were alsocharacterized by lower total SPQ scores than those reported previously for younger adults. Despite thepresence of age and sex-related differences in mean SPQ scores, a three-factor model of schizotypal person-ality best characterized the SPQ responses from mature adults, replicating that reported previously in high-school and university-aged samples. The implications of these findings of SPQ factor structure invariance,across age and gender, are discussed with reference to studies investigating neurocognitive correlates ofschizotypy (i.e. endophenotypes).� 2005 Elsevier Ltd. All rights reserved.

Keywords: SPQ; Factor analysis; Schizotypy; Ageing

0191-8869/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.paid.2005.06.015

* Corresponding author. Address: Centre for Clinical Research in Neuropsychiatry, Private Mail Bag, No. 1,Claremont, WA 6910, Western Australia. Tel.: +61 8 9347 6429; fax: +61 8 9384 5128.

E-mail address: [email protected] (J.C. Badcock).

mailto:[email protected]

78 J.C. Badcock, M. Dragovic / Personality and Individual Differences 40 (2006) 77–85

1. Introduction

Individual differences in schizotypal personality have commonly been explored as a means ofexamining the nature and structure of schizophrenia symptoms. Research on schizotypal person-ality in the general population may provide a particular opportunity to study the biological andcognitive markers of vulnerability to schizophrenia without the confounding effects of long termhospitalization, medication and severe psychotic symptoms (Raine & Lencz, 1995). A basicassumption of this approach is that the number and content of dimensions, or factors, describingthe features of schizotypal personality closely parallels those underlying subtypes of schizophre-nia. Whilst previous studies have favoured a multidimensional view of schizotypy there has beenconsiderable variation in the factor structures reported, raising doubts about how schizotypy isbest conceptualized and its relationship to the heterogeneity of schizophrenia. At least some ofthese discrepancies may have arisen as a result of the different statistical methods used (Fossati,Raine, Carretta, Leonardi, & Maffei, 2003; Rossi & Daneluzzo, 2002) or as a result of the differentassessment instruments employed (Reynolds, Raine, Mellingen, Venables, & Mednick, 2000). Inorder to better understand the hypothetical continuum between schizotypal personality andschizophrenia it is also necessary to examine the similarity of factor structures between thesetwo groups across a range of age-groups. This type of investigation would indicate whether thesesymptom structures, and underlying biological and cognitive mechanisms, are both comparableand stable traits across the lifespan (Sato, Bottlender, Schroter, & Moller, 2004). Whilst schizo-phrenia has a peak onset in late adolescence or early adulthood a sizeable minority of patientshave a later age of onset. Bleuler�s original criteria for late-onset schizophrenia (onset of illnessafter the age of 40 years), emphasized the similarity of symptom presentation to that of earlieronset schizophrenia, though some differences were also noted (Bleuler, 1943; Howard, Rabins,Seeman, & Jeste, 2000). However, as yet no studies have attempted to elucidate the factor struc-ture of symptoms in late-onset schizophrenia (Sato et al., 2004) and very few studies have exam-ined the factor structure of schizotypal features in healthy adults in middle or later years.

The Schizotypal Personality Questionnaire (SPQ; Raine, 1991) is used frequently to assess indi-vidual differences in vulnerability to schizophrenia (i.e. endophenotypes) in the general popula-tion. Previous factor analytic studies of the SPQ in normal samples have strongly supportedthe �disorganised three-factor model� of schizotypal personality (Raine et al., 1994; Rossi & Dane-luzzo, 2002). The characteristics of these three factors include Cognitive–Perceptual Dysfunction(Ideas of Reference, Magical Thinking, Unusual Perceptual Experiences, Suspiciousness); Inter-personal Deficits (Social Anxiety, No Close Friends, Suspiciousness and Constricted Affect)and Disorganization (Odd Speech and Odd Behaviour), which appear to be broadly comparablewith the three syndrome structure of schizophrenic symptoms (i.e. positive, negative and disorga-nized symptoms respectively). Somewhat different factor structures have been obtained whenexamining schizotypy through semi-structured interviews or other personality-related question-naires, consequently this study focussed on the factor structure underlying responses to the SPQ.

Relatively few studies have examined potential variations of SPQ factor structure and contentwith reference to the different characteristics of study samples, such as age, gender, education, eth-nicity etc. (Fossati et al., 2003; Raine et al., 1994; Reynolds et al., 2000). In particular, factorsknown to affect the timing and expression of schizotypal traits, namely age and gender, mightbe expected to yield systematic differences in factor structure. However, the majority of factor

J.C. Badcock, M. Dragovic / Personality and Individual Differences 40 (2006) 77–85 79

studies of SPQ have been conducted on young people (<25 years) (Gruzelier, 1996). For example,Fossati et al. (2003) directly compared the SPQ scores of adolescents (mean 16.4 years) and uni-versity students (mean 21.93 years) and concluded that the underlying factor structure is invariantwith age. However, the expression of schizotypal traits, and SPQ scores, also changes in olderadults; yielding a negative correlation between age and schizotypal features (Chen, Hsiao, &Lin, 1997). Both Wolfradt and Straube (1998) and Chen et al. (1997) have suggested that the dif-ferentiation of schizotypal symptoms may increase with age, possibly as a result of varying devel-opmental processes. Such age-related changes could, therefore, impact on the stability of the SPQfactor structure in older age groups. One study has replicated the disorganized three-factor struc-ture in mature adults (Chen et al., 1997). However, the authors noted that cultural inhibitions mayhave limited the expression of abnormal experiences; hence differentiation of schizotypal experi-ences in this older group may have been obscured. Based on these findings the primary goal of thisstudy was to assess age-related differences in the factor structure of SPQ responses from a mature,adult sample and compare our findings to those described in adolescent and young adult samples.

The expression of schizotypal symptoms in the general population also differs between the sexes(Maric, Krabbendam, Vollebergh, de Graaf, & van Os, 2003; Raine, 1992; Roth & Baribeau,1997) paralleling that seen in schizophrenia. Females tend to exhibit more positive schizotypalexperiences (auditory hallucinations, delusional beliefs) whilst negative schizotypal experiences(blunted affect, retarded speech) are more common in males. Similarly the age of onset of psy-chotic-like experiences occurs earlier in males than in females (Spauwen, Krabbendam, Lieb,Wittchen, & van Os, 2003) in line with that reported in epidemiological studies of schizophrenia(WHO, 1992). Spauwen et al. (2003) concluded that maturational events, with differential timingbetween the sexes may cause the expression of psychosis along the entire continuum (see alsoWalker & Bollini, 2002). An important implication of these studies is that age-related sex differ-ences in the factor structure of schizotypal symptoms may occur throughout adulthood. Very fewstudies have examined potential sex differences in schizotypy structure in older adults. Most re-cently, both Reynolds et al. (2000) and Fossati et al. (2003) concluded that the factor structureof the SPQ was invariant across gender. However, both of these studies employed samples inthe younger age range. Moreover, Reynolds et al. (2000) noted that factor loadings and correla-tions between males and females, even in their sample of young adults, could not be equated.These studies leave open the possibility that schizotypal symptoms become more clearly differen-tiated between males and females during ageing, with resulting variation in factor structure. A sec-ondary aim of our study was, therefore, to examine gender differences in the factor structure of theSPQ in a non-clinical sample of mature adults and to compare these findings to previously pub-lished data in younger individuals.

2. Method

2.1. Subjects

The sample consisted of 352 randomly selected adult participants from Perth in Western Aus-tralia. Participants were ascertained from entries listed in the metropolitan telephone directoryand, after initial contact, each respondent was invited to participate in the study. After obtaining

Table 1Demographic characteristics of the age-based subgroups and the whole sample

N Age Age range Male/female (%)

M SD

18–34 117 27.4 4.8 – 47.9/52.135–46 117 40.2 3.3 – 45.3/54.747–79 118 52.0 4.4 – 50.0/50.0Males 168 40.0 11.6 18–79Females 184 39.8 10.3 18–56

Total 352 39.9 10.9 18–79 47.7/52.3


informed consent, questionnaires were then mailed to the participants� residential addresses. Thecollection of data was carried out in collaboration with the Survey Research Centre of the Uni-versity of Western Australia. Out of 1172 individuals contacted, and who satisfied the inclusioncriteria (not younger than 18 yrs and English language competency), 356 returned questionnaires.Four of the returned questionnaires were unusable, hence the final sample size was 352. For thepurpose of examination of age related differences, the sample was separated into three age groups(18–34, 35–46, 47–79). The demographic characteristics of the total study sample, and the threesubgroups, are shown in Table 1. The study was approved by the Human Research Ethics Com-mittee at the University of Western Australia.

2.2. Measures

All study participants were administered the 74-item SPQ (Raine, 1991). This self-report ques-tionnaire was designed to yield a dimensional assessment of the nine features of Schizotypal Per-sonality Disorder listed in DSM-III-R (APA, 1987). This questionnaire has previously beenshown to have adequate reliability and validity. In particular the SPQ has acceptable internal con-sistency for the nine subscales (Cronbach�s a range = 0.71–0.78) and the total score (Cronbach�sa = 0.91).

3. Results

Data analysis comprised two stages. In the first stage the mean differences in manifest scores oneach SPQ sub-scale were analysed for males and females, and for the three age cohorts. In addi-tion, Cronbach�s alpha coefficients were calculated to explore the internal consistency of each SPQsub-scale. Secondly, confirmatory factor analysis was conducted to examine the latent structure ofthe SPQ. Having identified the best model, we compared its structural invariance across genderand the three age cohorts.

3.1. Descriptive statistics

Descriptive data for the SPQ sub-scales, and for total scale scores, are presented in Table 2. Theinternal reliability of the subscales was adequate (Cronbach�s a range = 0.59–0.82). The SPQ total

Table 2Schizotypal Personality Questionnaire descriptive statistics by sex and age groups

Male (n = 168) Female (n = 184) Age 6 34 (n = 117) Age 35–46 (n = 117) AgeP 47 (n = 118)

a M SD a M SD a M SD a M SD a M SD

Ideas of reference .79 1.60 2.03 .80 1.71 2.06 .82 2.15 2.38 .74 1.59 1.89 .78 1.23 1.71Social anxiety .80 2.37 2.24 .81 3.04 2.39 .82 2.68 2.42 .78 2.57 2.22 .82 2.91 2.38Odd beliefs .75 1.35 1.70 .72 2.08 1.81 .78 1.52 1.83 .73 1.86 1.84 .69 1.81 1.70Unusual perception .71 1.60 1.82 .79 1.91 2.10 .79 1.97 2.16 .75 1.75 1.96 .72 1.57 1.78Odd behaviour .74 1.01 1.50 .81 0.75 1.43 .77 1.03 1.56 .79 0.86 1.51 .76 0.71 1.33No close friends .79 2.65 2.43 .75 1.49 1.84 .79 1.90 2.17 .82 2.05 2.33 .76 2.17 2.16Odd speech .82 2.35 2.43 .75 2.40 2.13 .82 2.56 2.48 .77 2.39 2.22 .75 2.18 2.12Constricted affect .75 1.94 1.93 .59 1.05 1.28 .66 1.35 1.55 .77 1.53 1.78 .71 1.55 1.70Suspiciousness .78 1.73 1.96 .75 1.51 1.80 .77 1.76 1.96 .72 1.64 1.88 .76 1.45 1.79SPQ total score – 16.6 12.5 – 15.9 11.4 – 16.9 12.8 – 16.2 11.9 – 15.6 11.1

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score did not vary significantly between the three age cohorts in this sample (F[2,346] = 0.353;p = 0.703), however, it was significantly lower (t = 11.136; df = 1153; p < .001) than the totalSPQ score reported previously in younger adults (mean age 21.9 years) (Fossati et al., 2003). TotalSPQ scores did not differ significantly between the sexes in the full sample of mature adults(t = 0.530; df = 350; p = 0.596).

In the general linear model (GLM), SPQ subscales were considered as dependent variables, withsex (male versus females) and age cohorts (<34 years, 35–46 years, and >47 years) as factors.Based on Wilk�s Lambda criterion, GLM indicated multivariate between-group effects for sex(F[9, 338] = 12.87; p = <0.001; g2 = 0.255) and age groups (F[18,676] = 2.27; p = 0.002; g2 = 0.057).Univariate F-tests revealed that sex had an independent effect on several schizotypy subscales,with male subjects having higher scores than females on the two sub-scales (No Close Friendsand Constricted Affect), and having lower scores than females on the two sub-scales (Social Anx-iety and Odd Beliefs). For the majority of subscales age did not have an independent effect. Theonly exception was for the Ideas of Reference subscale, where in both sexes the score on this sub-scale decreased with age. This relationship was confirmed by calculating Pearson�s correlationcoefficient between these two variables (r = �0.18, p = 0.001). The interaction between sex andage group was non significant at the multivariate level (F[18,676] = 1.05; p = 0.396; g2 = 0.027),while univariate analysis of variance yielded a significant interaction for one sub-scale only. Onthe Odd Behaviour scale, male subjects showed a decrease in scores by age whereas female sub-jects showed an increase in scores by age.

3.2. Confirmatory factor analysis

Prior to analysis in LISREL, the data were analysed in PRELIS, where polychoric coefficientsand an asymptotic covariance matrix were generated. Because of the relatively small sample size,maximum likelihood (ML) estimation was used. The assessment of the fit of various models wasconducted using a scaled chi-square statistic (Satorra & Bentler, 1988), as this statistic corrects aninflated chi-square value due to non-normality, and is recommended for use in small samples(Curran, West, & Finch, 1996). Beside the chi-square statistic, which is sensitive to sample size,the fit of all subsequent scale modifications is assessed using several fit indices: (a) goodness offit index (GFI), (b) adjusted goodness of fit index (AGFI), (c) normed fit index (NFI) and(d) Akaike information criterion (AIC).

Table 3 presents the parameter estimates and fit statistics for several schizotypy models, includ-ing Raine�s three-factor model in both males and females, and in three age groups. Results of thecomparison of competing schizotypy models proposed in the literature confirmed that Raine�sthree-factor model was superior to other models.

Differences in chi-square measures of fit for the identical models between the sexes and threeage groups were not significant indicating that the model is resistant to sex and age variation.Since the assessment of Raine�s three factor model in males and females included some adultsin the younger age range 18–34 years the analysis was repeated for participants 34 years (malesn = 112; females n = 123) and older. The chi square values (males 41.23, females 50.36) and good-ness of fit index (GFI males 0.91, females 0.90) indicated that the three factor model was equallygood for adult males and females.

Table 3Goodness-of-fit indices for four models (N = 352) and for Raine�s model in both sexes and three age groups

x2 df p GFI Adj. GFI NFI AIC

Null 2144.23 36 0.00 – – – –One factor 376.66 27 0.00 0.75 0.59 0.80 551.18Simple two-factor 209.96 26 0.00 0.85 0.74 0.88 314.87Kendler two-factor 187.03 24 0.00 0.87 0.75 0.89 286.69Raine three-factor 118.50 23 0.00 0.91 0.83 0.93 162.50Male (n = 168) 62.45 23 0.00 0.90 0.81 0.93 106.45Female (n = 184) 70.14 23 0.00 0.91 0.82 0.93 114.1418–34 years (n = 117) 62.59 23 0.00 0.86 0.73 0.89 106.5935–46 years (n = 117) 53.43 23 0.00 0.89 0.79 0.91 97.4347–79 years (n = 118) 46.71 23 0.00 0.91 0.82 0.91 90.71

Note: df = degrees of freedom; GFI = goodness-of-fit index; Adj. GFI = Adjusted goodness-of-fit index; NFI =normed fit index; AIC = Akaike information criterion.


4. Discussion

The current findings confirm the view that the frequency of schizotypal experiences in olderadults is notably lower than that occurring in adolescence (Fossati et al., 2003; Chen et al.,1997). Despite this significant reduction in total SPQ scores, a three-factor model of schizotypalpersonality, comprising Cognitive–Perceptual Dysfunction, Interpersonal Deficits and Disorgani-zation, best characterizes the structure of schizotypy in mature adults. Furthermore, this resultwas demonstrated in each of the increasing age groups examined in the current study, confirmingthat the �disorganized three-factor model� previously described by Raine and colleagues, and oth-ers, in non-clinical samples (e.g. Gruzelier, 1996; Raine, 1991; Raine et al., 1994; Reynolds et al.,2000) is consistently observed in adolescents, university students, young adults and mature adults,i.e. it is highly invariant with age. Similarly, despite sex-related differences on selected sub-scalescores, the three factor structure was clearly replicated in both males and females, i.e. it is alsoinvariant across gender. Such findings lend no support to the notion that schizotypal symptomsbecome increasingly differentiated with age (Chen et al., 1997; Wolfradt & Straube, 1998) orthrough age-related sex differences (Spauwen et al., 2003), since the three factor structure appearsto be stable across younger and older samples.

Before considering the implications of these findings it is important to note that this study hassome limitations. The sample size is relatively modest and the method of recruitment of partici-pants in this study may have introduced a sample bias. Approximately 30% of individuals sur-veyed returned the completed questionnaires. The nature of the bias that this may haveintroduced is unknown.

The current findings have important theoretical and empirical implications. First, the resultsstrengthen the conceptual notion that schizotypy is a multidimensional rather than unitary con-struct, reflecting multiple cognitive and/or biological mechanisms. Furthermore, studies aimed atexamining the differential correlates of schizotypal sub-factors may usefully be extended to in-clude a wider variety of age groups, since the stability of the factor structure in mature individualssuggests that at least some of these neuropsychological, physiological or neuroanatomical


mechanisms may be operating throughout adulthood (i.e. are not restricted to adolescence orearly adulthood). For example, Gruzelier and Kaiser (1996) presented evidence that the Cogni-tive–Perceptual features of schizotypy are related to variations in pubertal development of synap-tic density. Based on the current findings it is reasonable to suggest that age-related changes(reductions) in synaptic density may impact on Cognitive Perceptual Dysfunction in older adults.The current findings also have important experimental implications in that studies investigatingthe differential correlates of schizotypal sub-factors are likely to produce inconsistent results ifbased on fewer (or more) than three subfactors; since correlates are likely to vary as a functionof both the number and the type of factors entered into the analysis.

Lastly, the similarities between the three factor structure of schizotypal personality and the po-sitive, negative and disorganized symptom structure identified in patients with schizophrenia fur-ther strengthens the conceptual notion of a continuity between schizotypal personality andschizophrenia in biological and cognitive processes. Based on this dimensional framework thesymptom syndromes in schizophrenia may represent exaggerations of physiological and psycho-logical functions in schizotypal personality in the normal population. Consequently, research fo-cused on schizotypal personality is often viewed as providing a window on the aetiologicalmechanisms underlying the heterogeneity of schizophrenia, including the search for the inheritedvulnerability state or �endophenotype� of schizophrenia. Previous studies have reported, for exam-ple, that elevated scores on the positive dimension of the SPQ, (i.e. Cognitive–Perceptual Dys-function) reflect the genetic vulnerability to schizophrenia (Vollema, Sitskoorn, Appels, &Kahn, 2002; Yaralian et al., 2000). However, the degree to which research on individual differ-ences in schizotypal personality can inform our understanding of the mechanisms underlyingschizophrenia rests heavily on demonstrating the similarity of the factor structure of schizotypalpersonality in healthy individuals with that observed in patients with schizophrenia. The currentfindings provide convincing support for this approach and adds to previous studies showing that athree factor model of schizotypy, measured with the SPQ, closely parallels that seen in schizophre-nia, and is invariant across age, sex, culture, religious affiliation, family adversity and psychopa-thology (Fossati et al., 2003; Reynolds et al., 2000; Rossi & Daneluzzo, 2002). Based on thesefindings we would also predict that a direct comparison between the structure of symptoms in pa-tients with early and late onset schizophrenia would strongly support a stable three-factor modelconsistent with the current results (Sato et al., 2004). Recent studies have explored age-related dif-ferences in cognitive decline in older schizophrenia patients (50 years plus) and have shown aninteraction between the aging process and the illness (Friedman et al., 2001). The current findingssuggest that the SPQ may provide a useful tool to directly examine the mechanisms underlying theonset or exacerbation of psychotic symptoms in older adults, including why some adults withincreased genetic vulnerability remain symptom free.

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