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Gender and schizotypal personality features
Person. indicid.0(/f Vol. 22. No. 3, pp. 411416, 1997 Copyright c 1997 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0191-8869/97 $17.00+0.00 SO191-8869(%)00205-X
Pergamon
GENDER
AND SCHIZOTYPAL Robert
PERSONALITY
M. Roth and Jacinthe
FEATURES
Baribeau*
Laboratory of Human Neuropsychology and Neurophysiology (LAHNN), Department of Psychology (DS-413). Concordia University, 7141 Sherbrooke Ouest, Montreal, Quebec, Canada H4B lR6 (Received 20 December 1995; receivedfor publicarion I October 1996) Summary-Schizotypal personality is argued to be part of a spectrum of schizophrenia-related disorders. While salient gender differences in the symptomatology of schizophrenics have been reported, data with regards to such differences in DSM-III defined schizotypal features are more limited. Right-handed male (N = 120) and female (N = 137) university students completed the Schizotypal Personality Questionnaire (SPQ), a self-report instrument designed to tap all nine features of DSM-III-R schizotypal personality disorder. Results revealed that males are significantly higher only on the Eccentric/Odd Behavior subscale, while females score higher on the Ideas of Reference, Odd Beliefs/Magical Thinking and Social Anxiety subscales, as well as the Cognitive-Perceptual Dysfunction and Interpersonal Deficits factors. Effect sizes tended to be small, with only the Social Anxiety subscale yielding a moderate effect. 0 1997 Elsevier Science Ltd. All rights reserved.
INTRODUCTION A growing body of literature indicates significant gender differences among schizophrenic patients in terms of a variety of biological variables, course, outcome, symptomatology and risk factors (Bardenstein & McGlashan, 1990; Flor-Henry, 1990; Goldstein, Santangelo, Simpson & Tsuang, 1990; Lewis, 1992; Raine, Harrison, Reynolds, Sheard, Cooper & Medley, 1990). In contrast to the extensive work with schizophrenics, limited research has been carried out on gender differences in schizotypal personality, as defined by Diagnostic and Statistical Manual of Mental Disorders (rev. 3rd edn; DSM-III-R; American Psychiatric Association, 1987) criteria. This information may be of salience given that schizotypal personality appears to be part of a spectrum of schizophrenia-related disorders with a common etiological basis (Torgersen, 1994). Research using diagnostic interviews has provided only limited evidence for gender differences in schizotypal personality disorder (SPD). Although some studies have reported a higher prevalence of SPD among male than female samples (Dahl, 1986; Gilbertson, McGraw & Brown, 1986; Maier, Lichterman, Klinger, Huen & Hallmayer, 1992; Zimmerman & Coryell, 1989), others have failed to replicate this finding (Golomb, Fava, Abraham & Rosenbaum, 1995; Reich, 1987). In addition, little information is provided on potential gender differences in the individual features of SPD, as evaluated using structured interviews. This may be of some importance as individual differences in positive and negative schizotypal features have been reported to have different strengths of association with schizophrenia (Torgersen, 1994) and both structural and functional frontal lobe integrity (Raine, Sheard, Reynolds & Lencz, 1992). Gender differences in the individual features of schizotypal personality have been investigated primarily by means of self-report questionnaires usually completed by students. The usefulness of studying non-clinical samples of schizotypals has been repeatedly demonstrated (Lezenweger, 1993). Many studies have reported gender differences on individual measures of schizotypal features. Men tend to score higher on ‘negative’ symptom measures such as the Physical and Social Anhedonia scales (Chapman, Chapman & Raulin, 1976; Muntaner, Garcia-Sevilla, Fernandez & Torrubia, 1988), and women score higher on the more ‘positive’ symptom scales such as Perceptual Aberration, Magical Ideation and Schizotypy (Chapman, Chapman & Raulin, 1978; Muntaner et al., 1988; Venables & Bailes, 1994). Men have also been found to score higher than women on scales reflecting an asocial aspect of schizotypal personality, such as the Eysenck Psychoticism Scale and Hypomanic Personality Scale (Bentall, Claridge & Slade, 1989; Eysenck & Eysenck, 1976). None of these scales,
*To whom all correspondence
should
be addressed. 411
412
Robert M. Roth and Jacinthe Baribeau
however, was specifically designed to tap all the salient phenomenological characteristics of SPD as DSM-III or DSM-III-R criteria. In particular, the psychosis-proneness and Eysenck Psychoticism scales appear to have limited convergent validity with questionnaires and structured interview designed to reflect SPD as defined by the DSM (Raine, 1987, 199 1). Gender differences have also been observed in studies in which a number of individual schizotypal and psychosis-proneness scales are factor-analyzed together. Such studies allow for the simultaneous evaluation of gender differences on multiple features of schizotypy, as well as the three to four separate factors of schizotypal personality that have emerged. Results of such investigations have generally confirmed reports based on individual scales, women scoring higher on positive symptom factors and men higher on negative symptom factors (Bentall, et al., 1989; Claridge, McCreery, Mason, Bentall, Boyle, Slade & Popplewell, 1996). The Schizotypal Personality Scale (STA), unlike the above measures, is based on DSM-III criteria (Claridge & Broks, 1984). Women tend to score higher than men on this scale. Recent factor analytic studies have reported that the STA loads highly on both positive and social anxiety/cognitive disorganization symptom factors of schizotypal personality (Bentall, et al., 1989; Claridge et al., 1996). To our knowledge, separate factors and/or individual features of SPD have not been reported to have corresponding factors and subscales within the STA. Thus, although the STA appears to be somewhat biased towards positive schizotypal features, further investigation is required in order to determine to what degree gender differences on the scale are differentially influenced by clusters of items related to positive and social anxiety/cognitive disorganization factors and features of schizotypal personality. Raine (1992) has recently provided more evidence for gender differences in DSM-III-R schizotypal personality features using the Schizotypal Personality Questionnaire (SPQ; Raine, 1991). The SPQ is a 74-item self-report questionnaire designed to assess all nine schizotypal features as defined in DSM-III-R. Adequate reliability and validity has been demonstrated (Raine, 1991). Three factors make up the SPQ: cognitive-perceptual dysfunction, interpersonal deficits and disorganization. This factor structure has been replicated and shown to hold for both males and females (Raine, Reynolds, Lencz, Scerbo, Triphon & Kim, 1994). Consistent with studies using incomplete assessments of schizotypal personality, results revealed that female college students score higher on the more positive symptom subscales of ides of reference and odd beliefs/magical thinking, as well as the cognitive-perceptual factor score. In contrast males score higher on the negative symptom subscales of no close friends and constricted affect, but no gender difference was observed on the interpersonal deficits factor score. These findings appear robust as they were replicated in a second sample. A more recent investigation also using the SPQ failed to detect higher scores for females on the positive features, but did find that men obtained higher scores on a number of the negative symptom subscales (Miller & Burns, 1995). The present study attempts to provide further evidence for gender differences in schizotypal personality features using a non-clinical sample. Since previous work has demonstrated a significant relationship between handedness and scores on the SPQ (Kim, Raine, Triphon & Green, 1992) and handedness was not controlled for in previous investigations using the SPQ, only right-handed individuals were assessed.
METHOD Subjects A total of 264 right-handed undergraduate university students volunteered to complete the SPQ. In order to maximize diversity within our sample, and reduce the potential bias that may be introduced by the common method of sampling of subjects from introductory psychology courses (Lezenweger & Korfine, 1992) the SPQ was distributed in undergraduate classes covering a wide variety of study areas, as well as in areas of the university in which heterogeneity of the population with regards to major is likely to be maximized (e.g. cafeteria). Handedness was determined by selfreport. The sample consisted of 137 women and 120 men between the ages of 18 and 26. The mean age of the men was 21.90 (SD = 1.95) years and 21.07 (SD = 1.92) years for the women.
Gender and schizotypal personality features Table
I. Means.
standard
deviations.
f-tests and effect sizes (d,l comparing factor
men (N = 121) and wanen
Cognitive-perceptual
Unusual
perceptual
Suspicious/paranoid Interpersonal
SD
f
rl
6.54
I I .99
5.89
-2.88
0.004’
0.36
3.19
2.52
3.98
2.41
-2.56
0.01 I’*
0.35
thinking
2.01
2.03
2.75
I .99
-2.98
0.003**
0.37
experiences
2.39
2.06
2.70
2.07
-
I.19
0.234
0.15
2.17
I.91
2.51
I .82
-
1.72
0.087
0.22
9.43
6.40
10.93
5.14
-2.06
0.041’
0.26
Factor
M
P
9.15
ideation
deficits
Women SD
factor
beliefs/magical
three
M
Ideas of reference Odd
(N = 138) on the nine subscales,
scores and total score of the SPQ
Me” Measure
413
2.12
I .83
I .99
I .60
0.61
0.542
0.08
No close friends
2.40
2.30
2.36
1.70
0.16
0.870
0.02
Social
2.74
2.12
4.02
2.20
0.001***
0.59
0.283
0.13
0.644
0.06
2.5 I
0.013****
0.3 I
1.93
0.054
0.25
Contricted
affect
anxiety
Disorganization
factor
Odd speech Eccentrtc/odd Total
behavior
SPQ sccwe
Note: **P
Significance < 0.0125,
levels within
for
the total
the interpersonal
SPQ
score
deficits
6.1 I
4.17
5.57
3.90
3.41
2.56
3.56
2.47
2.69
2.28
2.0 I
2.1
23.14
12.73
and
three
factor
***P
factors < 0.016,
*P < 0.05,
and within
I .08 -0.44
I
10.03
25.92 are
-4.66
for
-
subscales
the disorganization
within factor
the cognitive-perceptual ****P
factor
< 0.025.
Measure As indicated previously, the SPQ (Raine, 1991) is designed to assess all nine features of SPD. A three-factor solution has been found to be most appropriate for the SPQ, the factors being cognitiveperceptual dysfunction, interpersonal deficits and disorganization (Raine et al., 1994). The subscales that compose the cognitive-perceptual dysfunction factor are ideas of reference, odd beliefs/magical thinking, suspiciousness/paranoid ideation and unusual perceptual experiences. No close friends, constricted affect and social anxiety make up the interpersonal deficits factor. The disorganization factor is composed of the odd speech and eccentric/odd behavior subscales. Consistent with Raine (1992), factor scores were obtained by summing the scores of the individual subscales composing each factor. The SPQ has been found to have good psychometric properties (Raine, 1991; Raine et al., 1994). In particular, Raine (1991) has found that 55% of subjects scoring in the top 10% on the SPQ fulfil DSM-III-R criteria for SPD according to the Structured Clinical Interview for DSM-IIIR Personality Disorders (Spitzer, Williams & Gibbon, 1987).
RESULTS In order to permit a direct comparison of our results with those of Raine (1992), two-tailed ttests were performed on the nine subscale scores, three factors, and the total SPQ score. Effect sizes (d) were also calculated (Cohen, 1988). Since multiple r-tests are likely to inflate the probability of Type I error, significance level was set at P < 0.05 for comparisons involving the three factor and total SPQ scores. Bonferroni-adjusted alpha levels were used to evaluate the significance of individual schizotypal features within each factor. Alpha levels were 0.0125 (0.05/4) for the cognitive-perceptual factor, 0.016 (0.05/3) for the interpersonal deficits factor, and 0.025 (0.05/2) for the disorganization factor. Descriptive statistics, results of the t-tests and effect sizes are presented in Table 1. Women were found to score significantly higher than men on the ideas of reference (P = 0.01 l), odd beliefs/magical thinking (P = 0.003) and social anxiety (P = 0.001) subscales, as well as the cognitive-perceptual dysfunction (P = 0.004) and interpersonal deficits (P = 0.041) factors. A trend was also found indicating that women score higher than men on the total SPQ score (P = 0.054). Men scored significantly higher than women only on the eccentric/odd behavior subscale (P = 0.013). Effect sizes for the majority of these differences tended to be slightly above the 0.2 criteria for a small effect propounded by Cohen (1992). Only the effect size of 0.59 obtained for social anxiety could be considered a moderate effect (i.e. 0.5 to 0.8). DISCUSSION The present results are generally consistent with those reported women score higher than men on the more positive schizotypal
by Raine (1992). We found that characteristics, namely ideas of
414
Robert M. Roth and Jacinthe Bar&au
reference and odd ~liefs/magical thinking, as well as the cognitive-perceptual factor, The robustness of these findings is clear as they appear both in our study and Raine’s. With regards to the trend previously observed for males to score higher on eccentric/odd behavior, our results indicate a significantly greater score for males. As in previous investigations using the SPQ, no significant gender differences emerged for the unusual perceptual experiences and odd speech features. Thus our findings for the positive schizotypal features are consistent with those obtained by Raine, though discrepant with regards to Miller and Burns (1995). The latter study did not find gender differences on the cognitive-perceptual factor score or any of its features. Results for the negative features are inconsistent across investigations. In our sample women scored significantly higher than men on the interpersonal deficits factor. The opposite result was obtained by Miller and Burns. In addition, while both Raine and Miller and Burns found that males scored significantly higher on the negative features of no close friends and constricted affect, we did not find such differences and extremely small effect sizes. It is interesting to note that while there are important differences between our study and the others in terms of negative features, all three investigations report significantly greater social anxiety in females than males. A higher level of social anxiety in females is consistent with studies indicating greater manifestation of affective symptoms in female than male schizophrenics (Bardenstein & McGlashen, 1990). A trend was observed indicating that women, as a group, scored somewhat higher than men on the total SPQ score. We could not compare this finding to previous results on the SPQ as the other investigations did not provide this comparison. Another way of looking at the implications of this finding, however, is to determine how many of our subjects actually fulfil diagnostic criteria for SPD. Although we did not conduct diagnostic evaluations with our subjects, Raine (1991) found that 55% of subjects scoring above his 10% high-point cut-off total SPQ score of 41 ful~lled diagnostic criteria for SPD. In the present sample 5.4% of females and 10% of males obtained scores above this cut-off. It is therefore probable that in our sample almost twice as many males than females would fulfil diagnostic criteria for SPD. That as a group females had a higher mean total SPQ score, but individually are less likely than men to fulfil SPD diagnostic criteria, is consistent with studies reporting a higher prevalence of SPD among males (Dahl, 1986; Gilbertson et al., 1986; Maier et al., 1992; Zimmerman & Coryell, 1989). The present results offer strong support for the higher level of positive features observed in females in previous studies of schizotypal personality (Claridge & Hewitt, 1987; Raine, 1992), psychosis-proneness (Muntaner et al., 1988) and schizophrenia (Bardenstein & McGlashen, 1990; Castle & Murray, 1991). In contrast to the positive features, results for the negative schizotypai features fail to support previous investigations of student samples. Disagreement with regards to gender differences in negative features also characterises the schizophrenia literature, with some studies reporting more negative symptoms in males (Goldstein ei al., 1990; Haas, Sweeney, Keilp & Hein, 1989) and others finding no differences (Josiassen, Roemer, Johnson & Shagass, 1990). The reason(s) underlying the inconsistencies between our investigation and those of other groups using the SPQ (Miller & Burns, 1995; Raine, 1992) are unclear. All three studies employed undergraduate university students of comparable age. The cultures in which samples were obtained are also quite similar (U.S.A. and Canada). The SPQ and other schizotypy questionnaires have generally been designed with items sensitive to gender bias and social desirability removed during test construction (Chapman, Chapman & Kwapill, 1995; Raine, 1991). Gender differences in schizophrenic symptomatology do not appear to be largely accounted for by sex role expectations and social skills (Andia & Zisook, 1991). Nevertheless, the possible effects of other sociocultural factors on schizotypal symptomatology and responding to schizotypy questionnaires is deserving of more attention. In addition, while our sample is somewhat more limited in size, effect sizes are comparable to those reported by Raine (1992). Statistical control for multiple comparisons is more stringent in the present study and that of Miller and Burns than Raine’s investigation, However, even when an alpha level of 0.005 (used by Miller and Burns) is applied to the Raine’s results, little change in his interpretations are warranted. It is also unlikely that our use of only right-handed subjects can account for most of the differences between studies. Handedness had been previously found to be significantly related to the cognitive-perceptual factor and the odd speech subscale of the SPQ (Kim et al., 1992). None of the investigations using the SPQ has reported gender differences in odd speech, and only Miller and Burns failed to observe a significant effect on the cognitive-perceptual factor.
Gender and schizotypai personality features
415
The question of whether handedness has a differential influence for males and females on the cognitive-perceptual factor awaits investigation. Further exploration of variables that may interact with gender in producing differences in schizotypal features is clearly required.
The use of factor scores to group Ss for investigation is common in studies of schizophrenia and SPD. Such composite scores may mask potentially salient individual differences in the relationship between specific schizotypal features and other variables. As demonstrated in this and other studies, group differences on factor scores are unlikely to be reflected in all the individual features that make up a given factor. Using appropriate control over Type I error, studies of subgroups based on factor scores should therefore consider the independent contribution of subscales within each factor on the dependent measures under investigation. Consideration of the factors and features of schizotypal personality may also help understand gender differences in the performance of high schizotypes on experimental paradigms. It has been frequently observed that the relationship between schizotypy and a few experimental measures is stronger and more consistent for males than females (Claridge, Clark & Beech, 1992; Gruzelier, 1994). One such finding indicates that the relationship between schizotypy and performance on tests with different sensitivities to left and right hemisphere disturbance is significantly moderated by gender (Claridge et al., 1992; Gruzelier, 1994). Of particular pertinence, Gruzelier (1994) observed that this gender effect on variables related to hemispheric asymmetry was itself moderated by the type of schizotypal syndrome (corresponding to the positive, negative and disorganization factors, discussed in the current paper) prominent among Ss of each gender. A complex interaction between gender, syndrome and ex~rimental task has also been reported in studies of schizophrenic patients (Gruzelier, 1994). Such an interaction may at least partially account for the differential risk of males and females for the development and expression of negative and positive syndromes and particular symptoms of schizotypal personality and schizophrenia, as well as inconsistent findings on potential markers for schizophrenia.
REFERENCES American Psychiatric Association. (1987). Diagnostic and statistical manual of‘mental disorders (Ref. 3rd edn). Washington, DC: American Psychiatric Press. Andia, A. M. & Zisook, S. (1991). Gender differences in schizophrenia: A literature review, Annals ofclinical Psvchiuiry. 3, 333-340. Bardenstein, K. K. & McGlashan, T. H. (1990). Gender differences in affective, schizoaf%ctive and ~hizophrenic disorders: A review. Sch~zophrenja Research. 3, 159-l 72. Bentall, R. P., Claridge. G. S. & Slade, P. D. (1989). The multidimensional nature of schizotypal traits: A factor analytic study with normal subjects. British Journal of Clinical Psychology, 28.363-375. Castle, D. J. & Murray, R. M. (1991). The neurodevelopmental basis of sex differences in schizophrenia. Psychological Medicine, 21, 565-575.
Chapman, J. P., Chapman, L. J. & Kwapill, T. R. (1995). Scales for the measurement of schizotypy. In A. Raine, T. Lencz & S. A. Mednicj (Eds), SchizoIypalpersonaliry (pp. 79-106). New York: Cambridge. Chapman, L. J., Chapman J. P. & Raulin, M. L. (1976). Scales for physical and social anhedonia. Journal o/‘Abnormal Psychology, 85, 374-382.
Chapman, L. J., Chapman, J. P. & Raulin M. L. (1978). Body-image aberration in schizophrenia. Journal qf Abnormal Psychology, 87, 399-407.
Claridge, G. (1994). Single indicators of risk for schizophrenia: Probable fact or likely myth? Schizophrenia Bulletin, 20, I51168. Claridge, G. & Broks, P. (1984). Schizotypy and hemisphere function. I. Theoretical considerations and the measurement of schizotypy. Personu~jty and ~ndividuaf DiSferences, 5,633#8. Claridge, G. S., Clark, K. H. & Beech, A. R. (1992). Lateralization of the ‘negative priming’ effect: Relationship with schizotypy and with gender. British Journal of Psycholog~f, 83, 13-23. Claridge, G. & Hewitt, J. K. (1987). A biometric study of schizotypy in a normal population. Persona/& und ~ndizliduu~ Dijjkrences. 8, 303-3 12.
(1996). The factor structure of ‘schizotypal’ traits: A large replication study. British Journal @‘Clinical Psychology. 35. IO3-115. Cohen, J. (1988). Statisficalpower analysis for the behavioral sciences. Hillsdale, NJ: Erlbaum. Cohen, J. (1992). A power primer. Psychological Bulletin, 112. 155- I59. Dahl, A. A. (1986). Some aspects of the DSM-III personahty disorders illustrated by a consecutive sample of hospitalized patients. Arra Psychiawica Scandinavica, 228 (Suppl.), 61-67. Eysenck, H.J. & Eysenck, S. B. G. (1976). Psyrhoricism as a dimension qj’personalitJ_ London: Hodder 8~ Stoughton. Flor-Henry. P. (1990). Influence of gender as related to other psychopathological syndromes. Schizophrenia Bullefin, 16, 21 I-227. Gilbertson, A. D., McGraw, L. K. & Brown, N. E. (1986). A different empirical perspective on sex bias in the diagnosis of DSM-111 axis II disorders. Psychiatry Quarter/y, 58, 144147.
Claridge,G., McCreery, C., Mason, O., Bentall, R., Boyle, G., Stade, P. & Popplewell, D.
416
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M. Roth
and
Jacinthe
Baribeau
Goldstein, J. M., Santangelo, S. L., Simpson, J. C. & Tsuang, M. T. (1990). The role of gender in identifying subtypes of schizophrenia: A latent class analytic approach. Schjzophrenja BalIeiin, i&263-275. Golomb, M., Fava, M., Abraham, M. & Rosenbaum, J. F. (1995). Gender differences in personality disorders. Americun Journal qf Psychiatry, 132, 579-582. Gruzelier, J. H. (1994). Syndromes of schizophrenia and schizotypy, hemispheric imbalance and sex differences: Implications for developmental psychopathology. Internaiional Journal of Psychophysiology, 18, 167-178. Haas, G. L., Sweeney, J. A., Keilp. J. & Hein, D. A. (1989). Sex dsferences in neurocognition, Presented at the Annual Meeting of the American Psychological Association, San Francisco, CA, May. Josiassen, R. C.. Roemer, R. A., Johnson, M. M. & Shagass, C. (1990). Are gender differences in schizophrenia reflected in brain event-related potentials. Schkophrenia Bulletin, 16, 229-246. Kim, D., Raine, A., Triphon, N. & Green, M F. (1992). Mixed handedness and features of schizotypal personality in a nonclinical sample. Journal of Nervous and Mental Disease. 180, 131-I 33. Lewis, S. (1992). Sex and schizophrenia: Vive la difference. British Journal ofpsyehiutry, 161.445-450. Lezenweger, M. F. (1993). Explorations in schizotypy and the psychometric high-risk paradigm. In L. J. Chapman, J. P. Chapman & D. Dowles (Eds), Progress in e.~perjmentai personality and ps~~~hoputholog~research {Vol. 16, pp. 66-l 16). New York: Springer. Lezenweger, M. F. & Korfine, L. (1992). Confirming the latent structure and base rate of schizotypy: A taxometric analysis, Journal of Abnormal Psycholog.&>,IOf, 567-57 1. Maier, W., Lichterman, D., Klinger, T., Huen, R. & Hallmayer. J. (1992). Prevalence of personality disorders (DSM-III-R) in the community. Journal of Personal& Disorders, 6, 187-196. Miller, L. S. & Burns, S. A. (199.5). Gender differences in schizotypic features in a large sample of young adults. Journal qf Nervous and Mental Disease, 183, 657-661. Muntaner, C., Garcia-Sevilla, L., Fernandez, A. & Torrubia, R. (1988). Personality dimensions, schizotypal and borderline personality traits and psychosis proneness. Personality and Individual Differences, 9, 257-268. Raine, A. (1987). Validation of schizoid personality scales using indices of schizotypal and borderline personality disorder in a criminal population. British Journal of Clinical Psychology, 26, 305-309. Raine, A. (1991). The SPQ: A scale for the assessment of schizotypal personality based on DSM-III-R criteria. Schizophrenia Bulletin, I?‘, 555-564. Raine, A. (1992). Sex differences in schizotypal personality in a nonclinical population. Journal of Abnormal Psychology, IOI, 361-364. Raine. A., Harrison, G., Reynolds, G. P.. Sheard, C., Cooper, J. E. & Medley, J. (1990). Structural and functional characteristics of the corpus callosum in schizophrenics, psychiatric controls, and normal controls: An MRI and neuropsychological examination. Archives qf General Psychiatry, 47, 1060-1964. Raine, A., Reynolds, C., Lencz, T., Scerbo, A., Triphon, N. & Kim, D. (1994). Cognitive-perceptual. interpersonal, and disorganized features of schizotypal personality. Schizophrenia Bu/letin, 20, 191-201. Raine. A.. Sheard, C., Reynolds, G. P.. Lencz, T. (1992). Pre-frontal structural and functional deficits associated with individual differences in schizotypal personality. Schizophrenia Research, 7, 237-247. Reich, J. (1987). Sex distribution of DSM-III personality disorders in psychiatric outpatients. American JournalqfPsychiatry, 144,485-488. Spitzer, R. L., Williams, J. B. W. & Gibbon, M. (1987). Structured clinical interrie\c,for DSM-III-R personality disorders: SCID-II. New York: New York State Psychiatric Institute. Torgersen, S. (1994). Personality deviations within the schizophrenia spectrum. Arta P.yhia/rica Scandinarica, 90 (Suppl. 384). 40-44. Venables, P. H. & Bailes. K. (1994). The structure of schizotypy, its relation to subdiagnosis of schizophrenia and to sex and age. British Journal qf Clinical Psychology, 33. 277-294. Zimme~an. M. & Coryell, W. (1989). DSM-III personality disorder diagnoses in a nonpatient sample. Archives sf Generai Ps~c~?iatr~,46,682X%9.
Pergamon
GENDER
AND SCHIZOTYPAL Robert
PERSONALITY
M. Roth and Jacinthe
FEATURES
Baribeau*
Laboratory of Human Neuropsychology and Neurophysiology (LAHNN), Department of Psychology (DS-413). Concordia University, 7141 Sherbrooke Ouest, Montreal, Quebec, Canada H4B lR6 (Received 20 December 1995; receivedfor publicarion I October 1996) Summary-Schizotypal personality is argued to be part of a spectrum of schizophrenia-related disorders. While salient gender differences in the symptomatology of schizophrenics have been reported, data with regards to such differences in DSM-III defined schizotypal features are more limited. Right-handed male (N = 120) and female (N = 137) university students completed the Schizotypal Personality Questionnaire (SPQ), a self-report instrument designed to tap all nine features of DSM-III-R schizotypal personality disorder. Results revealed that males are significantly higher only on the Eccentric/Odd Behavior subscale, while females score higher on the Ideas of Reference, Odd Beliefs/Magical Thinking and Social Anxiety subscales, as well as the Cognitive-Perceptual Dysfunction and Interpersonal Deficits factors. Effect sizes tended to be small, with only the Social Anxiety subscale yielding a moderate effect. 0 1997 Elsevier Science Ltd. All rights reserved.
INTRODUCTION A growing body of literature indicates significant gender differences among schizophrenic patients in terms of a variety of biological variables, course, outcome, symptomatology and risk factors (Bardenstein & McGlashan, 1990; Flor-Henry, 1990; Goldstein, Santangelo, Simpson & Tsuang, 1990; Lewis, 1992; Raine, Harrison, Reynolds, Sheard, Cooper & Medley, 1990). In contrast to the extensive work with schizophrenics, limited research has been carried out on gender differences in schizotypal personality, as defined by Diagnostic and Statistical Manual of Mental Disorders (rev. 3rd edn; DSM-III-R; American Psychiatric Association, 1987) criteria. This information may be of salience given that schizotypal personality appears to be part of a spectrum of schizophrenia-related disorders with a common etiological basis (Torgersen, 1994). Research using diagnostic interviews has provided only limited evidence for gender differences in schizotypal personality disorder (SPD). Although some studies have reported a higher prevalence of SPD among male than female samples (Dahl, 1986; Gilbertson, McGraw & Brown, 1986; Maier, Lichterman, Klinger, Huen & Hallmayer, 1992; Zimmerman & Coryell, 1989), others have failed to replicate this finding (Golomb, Fava, Abraham & Rosenbaum, 1995; Reich, 1987). In addition, little information is provided on potential gender differences in the individual features of SPD, as evaluated using structured interviews. This may be of some importance as individual differences in positive and negative schizotypal features have been reported to have different strengths of association with schizophrenia (Torgersen, 1994) and both structural and functional frontal lobe integrity (Raine, Sheard, Reynolds & Lencz, 1992). Gender differences in the individual features of schizotypal personality have been investigated primarily by means of self-report questionnaires usually completed by students. The usefulness of studying non-clinical samples of schizotypals has been repeatedly demonstrated (Lezenweger, 1993). Many studies have reported gender differences on individual measures of schizotypal features. Men tend to score higher on ‘negative’ symptom measures such as the Physical and Social Anhedonia scales (Chapman, Chapman & Raulin, 1976; Muntaner, Garcia-Sevilla, Fernandez & Torrubia, 1988), and women score higher on the more ‘positive’ symptom scales such as Perceptual Aberration, Magical Ideation and Schizotypy (Chapman, Chapman & Raulin, 1978; Muntaner et al., 1988; Venables & Bailes, 1994). Men have also been found to score higher than women on scales reflecting an asocial aspect of schizotypal personality, such as the Eysenck Psychoticism Scale and Hypomanic Personality Scale (Bentall, Claridge & Slade, 1989; Eysenck & Eysenck, 1976). None of these scales,
*To whom all correspondence
should
be addressed. 411
412
Robert M. Roth and Jacinthe Baribeau
however, was specifically designed to tap all the salient phenomenological characteristics of SPD as DSM-III or DSM-III-R criteria. In particular, the psychosis-proneness and Eysenck Psychoticism scales appear to have limited convergent validity with questionnaires and structured interview designed to reflect SPD as defined by the DSM (Raine, 1987, 199 1). Gender differences have also been observed in studies in which a number of individual schizotypal and psychosis-proneness scales are factor-analyzed together. Such studies allow for the simultaneous evaluation of gender differences on multiple features of schizotypy, as well as the three to four separate factors of schizotypal personality that have emerged. Results of such investigations have generally confirmed reports based on individual scales, women scoring higher on positive symptom factors and men higher on negative symptom factors (Bentall, et al., 1989; Claridge, McCreery, Mason, Bentall, Boyle, Slade & Popplewell, 1996). The Schizotypal Personality Scale (STA), unlike the above measures, is based on DSM-III criteria (Claridge & Broks, 1984). Women tend to score higher than men on this scale. Recent factor analytic studies have reported that the STA loads highly on both positive and social anxiety/cognitive disorganization symptom factors of schizotypal personality (Bentall, et al., 1989; Claridge et al., 1996). To our knowledge, separate factors and/or individual features of SPD have not been reported to have corresponding factors and subscales within the STA. Thus, although the STA appears to be somewhat biased towards positive schizotypal features, further investigation is required in order to determine to what degree gender differences on the scale are differentially influenced by clusters of items related to positive and social anxiety/cognitive disorganization factors and features of schizotypal personality. Raine (1992) has recently provided more evidence for gender differences in DSM-III-R schizotypal personality features using the Schizotypal Personality Questionnaire (SPQ; Raine, 1991). The SPQ is a 74-item self-report questionnaire designed to assess all nine schizotypal features as defined in DSM-III-R. Adequate reliability and validity has been demonstrated (Raine, 1991). Three factors make up the SPQ: cognitive-perceptual dysfunction, interpersonal deficits and disorganization. This factor structure has been replicated and shown to hold for both males and females (Raine, Reynolds, Lencz, Scerbo, Triphon & Kim, 1994). Consistent with studies using incomplete assessments of schizotypal personality, results revealed that female college students score higher on the more positive symptom subscales of ides of reference and odd beliefs/magical thinking, as well as the cognitive-perceptual factor score. In contrast males score higher on the negative symptom subscales of no close friends and constricted affect, but no gender difference was observed on the interpersonal deficits factor score. These findings appear robust as they were replicated in a second sample. A more recent investigation also using the SPQ failed to detect higher scores for females on the positive features, but did find that men obtained higher scores on a number of the negative symptom subscales (Miller & Burns, 1995). The present study attempts to provide further evidence for gender differences in schizotypal personality features using a non-clinical sample. Since previous work has demonstrated a significant relationship between handedness and scores on the SPQ (Kim, Raine, Triphon & Green, 1992) and handedness was not controlled for in previous investigations using the SPQ, only right-handed individuals were assessed.
METHOD Subjects A total of 264 right-handed undergraduate university students volunteered to complete the SPQ. In order to maximize diversity within our sample, and reduce the potential bias that may be introduced by the common method of sampling of subjects from introductory psychology courses (Lezenweger & Korfine, 1992) the SPQ was distributed in undergraduate classes covering a wide variety of study areas, as well as in areas of the university in which heterogeneity of the population with regards to major is likely to be maximized (e.g. cafeteria). Handedness was determined by selfreport. The sample consisted of 137 women and 120 men between the ages of 18 and 26. The mean age of the men was 21.90 (SD = 1.95) years and 21.07 (SD = 1.92) years for the women.
Gender and schizotypal personality features Table
I. Means.
standard
deviations.
f-tests and effect sizes (d,l comparing factor
men (N = 121) and wanen
Cognitive-perceptual
Unusual
perceptual
Suspicious/paranoid Interpersonal
SD
f
rl
6.54
I I .99
5.89
-2.88
0.004’
0.36
3.19
2.52
3.98
2.41
-2.56
0.01 I’*
0.35
thinking
2.01
2.03
2.75
I .99
-2.98
0.003**
0.37
experiences
2.39
2.06
2.70
2.07
-
I.19
0.234
0.15
2.17
I.91
2.51
I .82
-
1.72
0.087
0.22
9.43
6.40
10.93
5.14
-2.06
0.041’
0.26
Factor
M
P
9.15
ideation
deficits
Women SD
factor
beliefs/magical
three
M
Ideas of reference Odd
(N = 138) on the nine subscales,
scores and total score of the SPQ
Me” Measure
413
2.12
I .83
I .99
I .60
0.61
0.542
0.08
No close friends
2.40
2.30
2.36
1.70
0.16
0.870
0.02
Social
2.74
2.12
4.02
2.20
0.001***
0.59
0.283
0.13
0.644
0.06
2.5 I
0.013****
0.3 I
1.93
0.054
0.25
Contricted
affect
anxiety
Disorganization
factor
Odd speech Eccentrtc/odd Total
behavior
SPQ sccwe
Note: **P
Significance < 0.0125,
levels within
for
the total
the interpersonal
SPQ
score
deficits
6.1 I
4.17
5.57
3.90
3.41
2.56
3.56
2.47
2.69
2.28
2.0 I
2.1
23.14
12.73
and
three
factor
***P
factors < 0.016,
*P < 0.05,
and within
I .08 -0.44
I
10.03
25.92 are
-4.66
for
-
subscales
the disorganization
within factor
the cognitive-perceptual ****P
factor
< 0.025.
Measure As indicated previously, the SPQ (Raine, 1991) is designed to assess all nine features of SPD. A three-factor solution has been found to be most appropriate for the SPQ, the factors being cognitiveperceptual dysfunction, interpersonal deficits and disorganization (Raine et al., 1994). The subscales that compose the cognitive-perceptual dysfunction factor are ideas of reference, odd beliefs/magical thinking, suspiciousness/paranoid ideation and unusual perceptual experiences. No close friends, constricted affect and social anxiety make up the interpersonal deficits factor. The disorganization factor is composed of the odd speech and eccentric/odd behavior subscales. Consistent with Raine (1992), factor scores were obtained by summing the scores of the individual subscales composing each factor. The SPQ has been found to have good psychometric properties (Raine, 1991; Raine et al., 1994). In particular, Raine (1991) has found that 55% of subjects scoring in the top 10% on the SPQ fulfil DSM-III-R criteria for SPD according to the Structured Clinical Interview for DSM-IIIR Personality Disorders (Spitzer, Williams & Gibbon, 1987).
RESULTS In order to permit a direct comparison of our results with those of Raine (1992), two-tailed ttests were performed on the nine subscale scores, three factors, and the total SPQ score. Effect sizes (d) were also calculated (Cohen, 1988). Since multiple r-tests are likely to inflate the probability of Type I error, significance level was set at P < 0.05 for comparisons involving the three factor and total SPQ scores. Bonferroni-adjusted alpha levels were used to evaluate the significance of individual schizotypal features within each factor. Alpha levels were 0.0125 (0.05/4) for the cognitive-perceptual factor, 0.016 (0.05/3) for the interpersonal deficits factor, and 0.025 (0.05/2) for the disorganization factor. Descriptive statistics, results of the t-tests and effect sizes are presented in Table 1. Women were found to score significantly higher than men on the ideas of reference (P = 0.01 l), odd beliefs/magical thinking (P = 0.003) and social anxiety (P = 0.001) subscales, as well as the cognitive-perceptual dysfunction (P = 0.004) and interpersonal deficits (P = 0.041) factors. A trend was also found indicating that women score higher than men on the total SPQ score (P = 0.054). Men scored significantly higher than women only on the eccentric/odd behavior subscale (P = 0.013). Effect sizes for the majority of these differences tended to be slightly above the 0.2 criteria for a small effect propounded by Cohen (1992). Only the effect size of 0.59 obtained for social anxiety could be considered a moderate effect (i.e. 0.5 to 0.8). DISCUSSION The present results are generally consistent with those reported women score higher than men on the more positive schizotypal
by Raine (1992). We found that characteristics, namely ideas of
414
Robert M. Roth and Jacinthe Bar&au
reference and odd ~liefs/magical thinking, as well as the cognitive-perceptual factor, The robustness of these findings is clear as they appear both in our study and Raine’s. With regards to the trend previously observed for males to score higher on eccentric/odd behavior, our results indicate a significantly greater score for males. As in previous investigations using the SPQ, no significant gender differences emerged for the unusual perceptual experiences and odd speech features. Thus our findings for the positive schizotypal features are consistent with those obtained by Raine, though discrepant with regards to Miller and Burns (1995). The latter study did not find gender differences on the cognitive-perceptual factor score or any of its features. Results for the negative features are inconsistent across investigations. In our sample women scored significantly higher than men on the interpersonal deficits factor. The opposite result was obtained by Miller and Burns. In addition, while both Raine and Miller and Burns found that males scored significantly higher on the negative features of no close friends and constricted affect, we did not find such differences and extremely small effect sizes. It is interesting to note that while there are important differences between our study and the others in terms of negative features, all three investigations report significantly greater social anxiety in females than males. A higher level of social anxiety in females is consistent with studies indicating greater manifestation of affective symptoms in female than male schizophrenics (Bardenstein & McGlashen, 1990). A trend was observed indicating that women, as a group, scored somewhat higher than men on the total SPQ score. We could not compare this finding to previous results on the SPQ as the other investigations did not provide this comparison. Another way of looking at the implications of this finding, however, is to determine how many of our subjects actually fulfil diagnostic criteria for SPD. Although we did not conduct diagnostic evaluations with our subjects, Raine (1991) found that 55% of subjects scoring above his 10% high-point cut-off total SPQ score of 41 ful~lled diagnostic criteria for SPD. In the present sample 5.4% of females and 10% of males obtained scores above this cut-off. It is therefore probable that in our sample almost twice as many males than females would fulfil diagnostic criteria for SPD. That as a group females had a higher mean total SPQ score, but individually are less likely than men to fulfil SPD diagnostic criteria, is consistent with studies reporting a higher prevalence of SPD among males (Dahl, 1986; Gilbertson et al., 1986; Maier et al., 1992; Zimmerman & Coryell, 1989). The present results offer strong support for the higher level of positive features observed in females in previous studies of schizotypal personality (Claridge & Hewitt, 1987; Raine, 1992), psychosis-proneness (Muntaner et al., 1988) and schizophrenia (Bardenstein & McGlashen, 1990; Castle & Murray, 1991). In contrast to the positive features, results for the negative schizotypai features fail to support previous investigations of student samples. Disagreement with regards to gender differences in negative features also characterises the schizophrenia literature, with some studies reporting more negative symptoms in males (Goldstein ei al., 1990; Haas, Sweeney, Keilp & Hein, 1989) and others finding no differences (Josiassen, Roemer, Johnson & Shagass, 1990). The reason(s) underlying the inconsistencies between our investigation and those of other groups using the SPQ (Miller & Burns, 1995; Raine, 1992) are unclear. All three studies employed undergraduate university students of comparable age. The cultures in which samples were obtained are also quite similar (U.S.A. and Canada). The SPQ and other schizotypy questionnaires have generally been designed with items sensitive to gender bias and social desirability removed during test construction (Chapman, Chapman & Kwapill, 1995; Raine, 1991). Gender differences in schizophrenic symptomatology do not appear to be largely accounted for by sex role expectations and social skills (Andia & Zisook, 1991). Nevertheless, the possible effects of other sociocultural factors on schizotypal symptomatology and responding to schizotypy questionnaires is deserving of more attention. In addition, while our sample is somewhat more limited in size, effect sizes are comparable to those reported by Raine (1992). Statistical control for multiple comparisons is more stringent in the present study and that of Miller and Burns than Raine’s investigation, However, even when an alpha level of 0.005 (used by Miller and Burns) is applied to the Raine’s results, little change in his interpretations are warranted. It is also unlikely that our use of only right-handed subjects can account for most of the differences between studies. Handedness had been previously found to be significantly related to the cognitive-perceptual factor and the odd speech subscale of the SPQ (Kim et al., 1992). None of the investigations using the SPQ has reported gender differences in odd speech, and only Miller and Burns failed to observe a significant effect on the cognitive-perceptual factor.
Gender and schizotypai personality features
415
The question of whether handedness has a differential influence for males and females on the cognitive-perceptual factor awaits investigation. Further exploration of variables that may interact with gender in producing differences in schizotypal features is clearly required.
The use of factor scores to group Ss for investigation is common in studies of schizophrenia and SPD. Such composite scores may mask potentially salient individual differences in the relationship between specific schizotypal features and other variables. As demonstrated in this and other studies, group differences on factor scores are unlikely to be reflected in all the individual features that make up a given factor. Using appropriate control over Type I error, studies of subgroups based on factor scores should therefore consider the independent contribution of subscales within each factor on the dependent measures under investigation. Consideration of the factors and features of schizotypal personality may also help understand gender differences in the performance of high schizotypes on experimental paradigms. It has been frequently observed that the relationship between schizotypy and a few experimental measures is stronger and more consistent for males than females (Claridge, Clark & Beech, 1992; Gruzelier, 1994). One such finding indicates that the relationship between schizotypy and performance on tests with different sensitivities to left and right hemisphere disturbance is significantly moderated by gender (Claridge et al., 1992; Gruzelier, 1994). Of particular pertinence, Gruzelier (1994) observed that this gender effect on variables related to hemispheric asymmetry was itself moderated by the type of schizotypal syndrome (corresponding to the positive, negative and disorganization factors, discussed in the current paper) prominent among Ss of each gender. A complex interaction between gender, syndrome and ex~rimental task has also been reported in studies of schizophrenic patients (Gruzelier, 1994). Such an interaction may at least partially account for the differential risk of males and females for the development and expression of negative and positive syndromes and particular symptoms of schizotypal personality and schizophrenia, as well as inconsistent findings on potential markers for schizophrenia.
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