Development of a version of the Schizotypy Traits Questionnaire (STA) for screening children

Schizophrenia Research 80 (2005) 253 – 261 www.elsevier.com/locate/schres

Development of a version of the Schizotypy Traits Questionnaire (STA) for screening children Eva Cyhlarova *, Gordon Claridge Department of Experimental Psychology, South Parks Road, Oxford OX1 3UD, United Kingdom Received 1 June 2005; received in revised form 29 July 2005; accepted 29 July 2005 Available online 19 September 2005

Abstract Schizotypy may be seen as both a dimension of normal individual differences and an indicator of the predisposition to schizophrenia and schizophrenia-spectrum disorders. Schizotypal traits have been widely investigated in adults but little research has explored schizotypy in younger samples. The aim of the present study was to examine the factor structure of schizotypal traits in a sample of normal children aged 11 to 15 years—a younger sample than investigated in the few previous studies. Schizotypal traits were assessed with the children’s version of the adult Schizotypy Traits Questionnaire (STA). A principal components analysis was carried out on data from 317 subjects and yielded a three-factor solution, similar to several previous studies of adult samples. Factor one was characterised by unusual perceptual experiences, factor two by paranoid ideation/social anxiety, and factor three by magical thinking. The factor structure of the STA of this young sample was comparable with the previous studies of adults. The findings suggest that the children’s version of STA is a scale suitable for the measurement of schizotypy in young populations, and that this scale could be useful in clinical assessment of children at risk for psychosis, as well as in research. D 2005 Elsevier B.V. All rights reserved. Keywords: Schizotypal traits; STA scale; Children; Factor analysis

1. Introduction It is well established that it is possible to recognise and measure bpsychotic-likeQ traits in healthy indivi* Corresponding author. Present address: University Laboratory of Physiology, Parks Road Oxford OX1 3PT, United Kingdom. Tel.: +44 1865 272455; fax: +44 1865 272469. E-mail address: [email protected] (E. Cyhlarova). 0920-9964/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.schres.2005.07.037

duals. Claridge (1997) proposed that these schizotypal traits form part of normal personality dimension, not necessarily in the pathological domain, while also representing characteristics which may indicate a predisposition to psychotic disorders. This approach is based on the dimensional view of abnormality, suggesting a continuum of variation describing predisposition to psychotic breakdown (Claridge, 1987, 1995). Schizotypy scales assess personality traits which are common in the general population (Verdoux and van

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Os, 2002), although many of the items, if taken to their extreme form, would resemble schizophrenia symptoms. A number of scales have been developed to assess schizotypal characteristics in the general population (Chapman et al., 1976, 1978; Claridge and Broks, 1984; Eckblad and Chapman, 1983, 1986; Eysenck, 1975; Golden and Meehl, 1979; Launay and Slade, 1981; Mason et al., 1995; Nielsen and Petersen, 1976; Rust, 1987; Venables et al., 1990). We selected for study here the Schizotypy Traits Questionnaire (STA scale, as it has come to be known in the literature and as it will be referred to here); the adult version was constructed by Claridge and Rawlings and reported by Claridge and Broks (1984). The STA scale is a 37item self-report questionnaire derived from the criteria for Schizotypal Personality Disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM-III; American Psychiatric Association, APA, 1980). There are several reasons for selecting the STA as the starting point for the development of a children’s schizotypy scale. Firstly, the STA has been extensively used and validated by experimental measures. These include divided visual field tasks (Broks et al., 1984), techniques using the negative priming paradigm (Beech and Claridge, 1987; Beech et al., 1989; Ferraro and Okerlund, 1996), and handedness (Claridge et al., 1998; Richardson, 1994). The scale strongly differentiated healthy control subjects from individuals with a history of psychotic illness, establishing the criterion validity of the scale (e.g. Jackson and Claridge, 1991). Secondly, test–retest analyses of the STA in normal subjects reveal high correlations, suggesting that the scale is a valid measure with good long-term stability (Jackson and Claridge, 1991; Muntaner et al., 1988). Thirdly, a number of studies reported high correlations of STA with other scales, e.g. with the Chapman scales (Bentall et al., 1988; Kelley and Coursey, 1992; Muntaner et al., 1988; Raine and Allbutt, 1989). Furthermore, several researchers have proposed that as a single scale for assessment of schizotypy, the STA provides the best measure of the underlying dimension (Kelley and Coursey, 1992; Raine and Allbutt, 1989). Although STA is a single scale aimed mainly at the bpositiveQ aspects of schizotypy, factor analytic studies of the adult STA items reveal a pattern of variability and confirm the heterogeneity of positive

schizotypy. Several such analyses have been published. Hewitt and Claridge (1989) reported three main factors in a general population sample: bMagical ThinkingQ, bUnusual Perceptual ExperiencesQ, and bParanoid Ideation and SuspiciousnessQ. In another adult study, Joseph and Peters (1995) replicated the three-factor structure of the STA. Wolfradt and Straube (1998) also reported three factors in an adolescent sample, but magical ideation and unusual perceptual experience formed a single factor, while social anxiety and suspiciousness split into two components. In a large sample of adults, Rawlings et al. (2001) reported four factors similar to those Hewitt and Claridge (1989) had described in males: magical thinking, paranoid suspiciousness (with feelings of isolation), unusual perceptual experiences, and social anxiety/sensitivity to criticism. Most of the schizotypy research using these scales have concentrated on adults, in particular on schizophrenic or schizotypal samples and their relatives. Nonetheless, it has been shown that children who later develop schizophrenia differ from controls in cognitive and behavioural functioning, many years before the onset of the illness (Crow et al., 1995; Gruzelier and Kaiser, 1996; Isohanni et al., 2000, 2001). Scales assessing similar constructs to the STA, e.g. the Perceptual Aberration Scale and Magical Ideation Scale (Chapman et al., 1978; Eckblad and Chapman, 1983) have been shown to have good long-term predictive validity. Several studies have reported that high scores on these scales in student samples predicted psychosis, schizotypal symptoms and psychotic-like experiences in 10-year follow up (Chapman et al., 1994; Kwapil, 1998; Kwapil et al., 1997, 2000). Both retrospective and prospective studies indicate an increase in the rate of psychiatric symptoms and adjustment problems beginning in early adolescence (Erlenmeyer-Kimling, 2001; Walker et al., 1996a,b). The initial manifestation of poor adjustment usually follows the onset of puberty (Walker and Bollini, 2002), and the positive and negative symptoms increase exponentially as the individual passes through adolescence and approaches early adulthood (Galdos and van Os, 1995). It has also been demonstrated that schizotypal personality disorder (SPD) exists in children (Meijer and Treffers, 1991; Wolff,

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1991a,b; Wolff et al., 1991), but childhood SPD has not received much attention in the literature. It seems reasonable to focus on schizotypy in children, as it is necessary to concentrate on development during or before adolescence in order to attempt to uncover the processes of neurodevelopment that are associated with these disorders (Walker and Bollini, 2002). The majority of studies use familial relationships to identify individuals (especially children) at risk (e.g. Cornblatt et al., 2002). Questionnaires assessing schizotypy allow for selection of individuals on the basis of self-report of schizotypal traits, and some studies have addressed schizotypy in healthy young populations. However, most of these applied adult scales to adolescents (e.g. BarrantesVidal et al., 2003; Rosa et al., 2000). Only very few attempted to specifically develop scales for younger samples, and these were older adolescent samples rather than children, and also included small numbers of subjects (DiDuca and Joseph, 1999; Rawlings and MacFarlane, 1994; Wolfradt and Straube, 1998). The purpose of the present study was to investigate schizotypy in a large sample of children from the general population. The aim was to examine the factor structure of the children’s version of the STA scale in a large sample, and refine the items according to the

factorial structure. It was important to use a reliable scale, in order to find out if measurement of these traits can be extended from adults to children, and to compare the factorial structure of schizotypy in children with studies of adults. Based on content and length of the scale, and support for the adult version in the literature, it was decided that the children’s version of the STA scale would be the most suitable as the basis for measuring schizotypy in children. This version of the STA scale had previously been used in small-scale student projects, but the scale has good face and content validity. This is the fist time it has been employed in a largescale study.

2. Method 2.1. Subjects The sample consisted of 317 pupils (196 boys, 121 girls) obtained from the general population of six mainstream Oxford schools, with no prior screening for mental health problems. All participants were between 11 and 15 years old (mean = 13.3, SD 1.2).

60

50

40

30

20

10

Std. Dev = 6.43 Mean = 18.9 N = 317.00

0 2.5

7.5 5.0

12.5 10.0

17.5

15.0

22.5

20.0

255

27.5 25.0

32.5

30.0

STA Score Fig. 1. Distribution of STA scores.

35.0

37.5

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Table 1 Descriptive statistics of children’s STA

Male Female Total

N

Mean

SD

Range

Skewness

196 121 317

18.2 20.0 18.9

6.3 6.5 6.4

3–37 4–34 4–37

0.020 0.284 0.112

2.2. Measures The participants completed the children’s version of the STA scale (Claridge and Broks, 1984); see Table 2. Claridge slightly re-worded the adult scale, in order to make it suitable for use with children. The items of this children’s version are very similar to the original STA (see Table 2). The STA items are scored byes/noQ with total scores ranging from 0 to 37. The questionnaire was administered as a part of a large investigation of cognitive function in children (Cyhlarova, 2002). 3. Results The children’s STA was approximately normally distributed (See Fig. 1). Table 1 shows the means and distributions of STA scores for girls and boys. On average, girls had a significantly higher score of 20.0 compared to boys, whose mean group score was 18.2 (t = 2.40, p = 0.017). The mean

scores of this sample were similar to the youngest reported groups of the adult STA (16 to 20 years) where males had mean scores of 18.2 and females 18.6 (Claridge, 1997). 3.1. Factor analysis The aim of the factor analysis was to assess components of the STA scale and then to compare the factorial structure of the scale in children with studies of adolescents (Wolfradt and Straube, 1998) and adult populations (Hewitt and Claridge, 1989; Joseph and Peters, 1995; Rawlings et al., 2001). Principal components analysis was conducted on the 37item children’s STA scale for boys and girls together using Statistical Package for the Social Sciences (SPSS). Thirteen factors with eigenvalues greater than 1 were extracted, accounting for 57.68% of the variance. The scree plot shown in Fig. 2 was very similar to the original adult study by Hewitt and Claridge (1989). As the plot suggested an elbow at the third factor, a three-factor solution with Varimax rotation was tested, which accounted for 24.45% of the variance. Item loadings are shown in Table 2. Using a loading of 0.3 as the criterion for significance, the three factors extracted were as follows: The first general factor, Unusual Perceptual Experiences (14 items), was characterised by perceptual aberration, bearing some resemblance to milder forms of psychotic-like symptoms such as hallucinations. This factor was very similar to the Unusual Perceptual Experiences factor found by Hewitt and Claridge (1989) and Joseph and Peters (1995). The second factor,

6

5

Eigenvalue

4

3

2

1

0 1

3

5

7

9

11 13 15 17 19 21 23 25 27 29 31 33 35 37

Component Number Fig. 2. Scree plot of STA children’s scores.

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Table 2 Item loadings for the three-factor solution Item

30 5 34 11 42 31 17 22 37 27 43 25 14 6 18 19 29 47 46 41 33 38 35 2 7 21 15 45 39 1 23 9 26 49 10 3 13

Have you ever thought you heard someone talking and then found it was some other noise? Does your own voice ever seem distant, faraway? Do you ever feel that your thoughts are not your own? Have you ever felt when you looked in a mirror that your face looked different? Are your thoughts sometimes so strong that you can almost hear them? When you are talking do you ever find that your thoughts stop suddenly? Do everyday things sometimes seem bigger or smaller than usual? Do you sometimes feel you can smell quite ordinary things more than usual? Do you think that accidents can be caused by evil spirits? Do you ever feel that sounds you don’t usually notice make it difficult for you to concentrate? When you go into a new place have you ever felt that you have been there before, even though you know you haven’t really? Have you ever felt that part of your body is changing shape? Do things sometimes seem as if they are not real? Does it often happen that almost every thought you have straightaway makes you think of a lot of other ideas? Are you often bothered by the feeling that other people are watching you? Do you find you can’t easily share your feelings with others? Do you ever feel frightened for reasons that you don’t understand? Are your feelings very easily hurt if someone speaks sharply to you? Do you often daydream so much it interferes with what you are trying to do? Do you ever feel that what you say is difficult to understand because the words are all mixed up and don’t come out right? Do you feel that you can’t let yourself go even with your friends? Do you sometimes feel that people are talking about you behind your back? When you’re in a room full of people do you often find it difficult to follow what the person you are with is saying? Do you often feel that other people have it in for you? Do you ever feel that you can’t stand very loud noise or very bright light? Do you hate going on your own into a room full of people? Do you feel lonely most of the time even when you are with other people? Have you ever felt that you could tell what another person was thinking? Do you believe that dreams can come true? Do you believe that people can tell what other people are thinking? Are you sometimes sure that other people can tell what you are thinking? Do you often have nightmares that wake you up? Do you ever feel sure that something is about to happen even though there doesn’t seem to be any reason for your thinking that? Do you ever get nervous when someone is walking behind you? Do you have bad tummy-ache when you are worried or upset? When in the dark do you often see shapes and forms even though there’s nothing there? Do you feel that it’s safer to trust nobody?

Paranoid Ideation/Social Anxiety (12 items), was also clearly defined, and comprised paranoia and suspiciousness items and items tapping social anxiety. This component

Factor I

Factor II

Factor III

Unusual perceptual experiences

Paranoid ideation/Social anxiety

Magical thinking

59 51 48 46 46 44 41 40 39 35 35 34 33 31 52 50 50 44 43 43 42 41 41 40 38 33 66 55 49 45 44 43 35 34

resembled the Paranoid Ideation and Suspiciousness factor previously reported (Hewitt and Claridge, 1989), but combined features of factor 2 (paranoid suspiciousness) and

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factor 4 (social anxiety) from the study by Rawlings et al. (2001). The third factor, Magical Thinking (8 items), was characterised by magical ideation and beliefs, resembling the Magical Thinking factor of Hewitt and Claridge (1989). Table 2 summarizes there three factors. Statistics for the bsubscalesQ are given in Table 3. When subscale scores were computed by summing the appropriate item responses, Unusual Perceptual Experiences was positively correlated with Paranoid Ideation/ Social Anxiety (r = 0.35) and also with Magical Thinking (r = 0.45), and the latter two subscales were also positively correlated (r = 0.42). Alpha coefficients were calculated for the full STA and the three subscales, indicating that internal consistency was very high. The alpha coefficient for the full STA was 0.82, for the Unusual Perceptual Experiences subscale 0.71, for Paranoid Ideation/Social Anxiety 0.69, and for Magical Thinking 0.63. The alpha coefficient could not be increased by removal of any of the items. Inspection of the items making up each factor showed that all of the Hewitt and Claridge (1989) eight items of Unusual Perceptual Experiences subscale loaded N0.3 on the first factor. In addition, three items (17, 22, 27) tapping perceptual aberration loaded N 0.3 on this factor, as did one item (31) tapping thought disorder. Seven of the original eight items of Paranoid Ideation and Suspiciousness subscale loaded N0.3 on factor 2. Five other items loaded on this factor: one of Hewitt and Claridge’s Magical Thinking (29), two tapping sensitivity (7, 47), and two relating to mild thought disorder (items 41, 46). Of the eight items of Magical Thinking subscale, six loaded N 0.3 on the third factor. Three other items loaded high on this third factor; one tapping perceptual aberration (9), one suspiciousness (49) and one psychosomatic tendencies (10). Factor scores were calculated for each individual on each factor. Pearson correlations of age with the three subscales were carried out. Age correlated negatively with one of the subscales: Unusual Perceptual Experiences (r = 0.12, p b 0.05). Sex differences were investigated for each of the subscales using t-tests (see Table 4). Consistent with findings for the full STA, females scored higher on Paranoid Table 3 Means, SDs, skewnesses, kurtoses and alpha coefficients (N = 317) Unusual perceptual experiences No. of items Means SD Skewness Kurtosis Alpha coefficient

14 7.0 3.1 0.20 0.62 0.71

Paranoid ideation/Social anxiety 12 6.8 2.7 0.21 0.52 0.69

Magical thinking 8 4.1 2.0 0.02 0.78 0.63

Table 4 Means and SDs of subscales by sex

Unusual perceptual experiences Paranoid ideation/Social anxiety Magical thinking

Sex

N

Mean

SD

Male Female Male Female Male Female

194 116 194 117 194 116

6.86 7.12 6.40 7.32 3.88 4.42

3.01 3.14 2.73 2.60 1.99 2.09

Ideation/Social Anxiety (t = 2.94, p b 0.01) and Magical Thinking subscales (t = 2.27, p b 0.05). Despite the large sample size, there was no significant sex difference for Unusual Perceptual Experiences (t = 0.74, p = 0.46).

4. Discussion The present study set out to measure schizotypal traits in a large sample of children, with the aim to examine the factor structure of the children’s version of the STA scale. The children’s version of the STA scale was used to assess schizotypal traits, because the original, adult STA scale (Claridge and Broks, 1984) has been successfully used and validated by experimental measures (e.g. Beech and Claridge, 1987; Ferraro and Okerlund, 1996), has shown good reliability (e.g. Jackson and Claridge, 1991; Muntaner et al., 1988) and high correlations with other scales (e.g. Bentall et al., 1988; Kelley and Coursey, 1992; Raine and Allbutt, 1989). The results were very satisfactory: there was a normal distribution of STA scores, with means consistent with age-related norms for the adult scale (Mason et al., 1995). Also the sex differences were similar to those found in adult studies (Bentall et al., 1989; Venables and Bailes, 1994): females scored higher than males, which was predicted as the STA taps mainly positive aspects of schizotypy, known to be more pronounced in females (Raine, 1992; Rawlings et al., 2000). It may also correspond to the sex difference typically observed in schizophrenic symptomatology: men show a consistent predominance of negative symptomatology (withdrawal and social isolation), whereas women tend to show more positivesymptom characteristics, such as affective symptoms (Bardenstein and McGlashan, 1990; Goldstein and Link, 1988; Goldstein et al., 1989; Mueser et al., 1990).

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The factor analysis of the children’s STA scale, performed for the first time in such a young sample, demonstrated a very similar factor structure for STA to that previously found in studies of adults (Hewitt and Claridge, 1989; Joseph and Peters, 1995). The three extracted factors were Unusual Perceptual Experiences, Paranoid Ideation/Social anxiety and Magical Thinking. The only slight difference in the factor structure obtained by previous studies of adult and adolescent samples and the present results was that social anxiety items loaded on the second factor with paranoid thinking, which would be expected, as these characteristics often co-exist (Hewitt and Claridge, 1989). Overall, the factor structure of STA in this sample of children closely resembled findings of previous adult studies. However, it should be noted that one cannot fully compare the multidimensionality of schizotypy from the analysis of items in a single scale, as opposed to cases where scales were the subject of the analysis (e.g. Claridge et al., 1996). In the latter study a diversity of scales was analysed, leading eventually to the construction of the authors’ four-scale Oxford– Liverpool Inventory of Feelings and Experiences (OLIFE; Mason et al., 1995). There is a similarity here to some O-LIFE factors—e.g. Unusual Experiences— but not to others, such as Cognitive Disorganisation. In our item analysis, the closest to Cognitive Disorganisation was the Paranoid Ideation/Social Anxiety factor. Several conclusions can be drawn from the present study. Firstly, schizotypy is indeed a measurable construct in younger subjects than has previously been shown. Secondly, the children’s version of the STA scale is a good measure of these traits in children. Thirdly, the factor structure of this scale is comparable in children and adults. In other words, the results suggest that schizotypal characteristics are present before puberty, and that the STA children’s scale is a reasonable measure to assess these characteristics. One disadvantage of the STA scale is the fact that it does not include items covering the bnegativeQ schizotypal traits, as the scale was derived from the DSM diagnostic criteria for SPD. Perhaps this issue could be addressed in future studies. There is a need for further study of non-clinical schizotypy in children, both as a dimension of normal personality variation and as a means of understanding developmentally

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prior processes foreshadowing schizophrenia-spectrum disorders. The adult STA has been widely employed to investigate correlates of schizotypy in adults, and the children’s STA scale could prove useful in similar experimental and follow-up studies of children (Cyhlarova, 2002). Some studies have already shown good long-term predictive validity of similar scales in adults (Chapman et al., 1994; Kwapil, 1998; Kwapil et al., 1997, 2000), and the children’s STA could be very useful in high-risk research studies, as well as in clinical assessments. One major as yet unanswered question is the extent to which these schizotypal traits in children or adults may represent not only a measure of individual differences but also an index of risk for future psychopathology. Assessing these traits in children and a long-term follow-up into adulthood might help answer this very important issue, which may perhaps bring us closer to successful intervention and prevention of psychotic breakdown.

Acknowledgements The authors would like to thank Rachel Reeves and Kathleen Taylor for their very helpful suggestions, and Paul Montgomery and Alex Richardson for their comments.

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