Psychometric properties of the Greek version of the Schizotypal Personality Questionnaire (SPQ) in young male obligatory conscripts: A two years test–retest study
Introduction
The study of the schizotypal personality traits in apparently normal individuals has received great attention due to genetic and epidemiological studies demonstrating that the schizotypal features cluster in subjects with elevated risk for schizophrenia and prodromal to the subsequent full manifestation of schizophrenia (review by Maier, Falkai, & Wagner, 1999). Two major theoretical approaches exist to explain the link between the schizotypal traits and schizophrenia. The theory of “schizotaxia” of Meehl (1962) proposes that schizotaxia is a conjectured neural integrative defect due to a dominant schizogene that gives rise to the schizotypal personality. This genetic profile implies vulnerability to schizophrenia and in synergy with other polygenic potentiators and adverse life experiences gives rise in a small percentage of these individuals to the clinical syndrome of schizophrenia.
Another theoretical approach to schizotypal traits favoured by Eysenck (Eysenck & Eysenck, 1976) states that personality traits such as those that define psychoticism are a continuum from health to schizophrenia with no need to introduce arbitrary cut off points above which schizotypal traits lay as a different entity (Claridge, 1994). According to this view certain dimensions of personality can be found in the general population and their extremes lead to the symptoms of a disease state such as schizophrenia (van Os, Hanssen, Bijl, & Ravelli, 2000).
Self-administered questionnaires have been used extensively in several studies examining the schizotypal personality traits. A self-administered questionnaire that assesses all nine aspects of the SPD according to the Diagnostic and Statistical Manual of Mental Disorders Revised DSM-III-R (American Psychiatric Association, 1987) is the Schizotypal Personality Questionnaire (SPQ) developed by Raine (1991). It can be used as a screening instrument in the general population for the identification of individuals with broad schizotypal traits (according to the author, 55% of top SPQ scorers obtained an interview-based SPD diagnosis), and may serve as a measure of individual differences in the schizotypal personality.
As part of the ASPIS, the aim of the current study was to assess the psychometric properties of the Greek version of the SPQ in a large unselected sample of apparently healthy young males who are on the one hand at an age of heightened risk for schizophrenia and on the other experiencing a stressful change in life circumstances (Stefanis et al., 2004).
Section snippets
Participants
The translated inventories SCL-90-R (Derogatis, 1993), SPQ and PAS (Chapman, Chapman, & Raulin, 1978) were administered (in this order) to 2243 randomly selected young male conscripts aged 18–24 years who were recruited from the Greek Air Force, during their first two weeks of admission in the National Basic Air Force training centre in the city of Tripoli. A team of military medical doctors of all specialties had already evaluated the conscripts as having a satisfactory medical condition,
Descriptive indices and internal reliability
Descriptive indices and alpha coefficients for the subscales and total SPQ are presented in Table 1 for the first assessment sample (along with the corresponding indices for the random responders whose missing values were not exceeded by 20% of the SPQ items: 420 individuals). The lower and upper cut off scores (ten-tiles) of the total SPQ scores were found equal to 12 and 44, respectively. Cronbach’s alpha coefficient was high (0.91) for the total score and satisfactory for the subscales
Discussion
The primary aim of this study was to assess the reliability and validity of the Greek version of the SPQ. Further, the psychometric indices of the PAS and SCL-90-R scales were estimated concurrently.
In the first assessment sample three of the SPQ subscales had moderate alpha coefficients (0.58–0.63) and noticeably lower than the corresponding ones in Raine’s samples (Table 1). Furthermore, the item 49 (writing letters to friends is more trouble than it is worth) had low item-scale correlation
Methodological limitations
Our sample consisted of young males that were recruited in the military service. Thus it cannot be claimed that our findings could be directly generalized to the Greek population (men and women of every age). Both age and gender are consistently reported to modify the SPD measurements. In particular, age is reported to be negatively correlated with the SPQ scores while males score significantly higher on negative symptom subscales than females and significantly lower on positive ones (Raine,
References (24)
- et al.
Increased psychophysiological arousal and orienting at ages 3 and 11 years in persistently schizotypal adults
Schizophrenia Research
(2002) - et al.
Variation in catechol-o-methyltransferase val158 met genotype associated with schizotypy but not cognition: a population study in 543 young men
Biological Psychiatry
(2004) - et al.
Strauss (1969) revisited: a psychosis continuum in the general population?
Schizophrenia Research
(2000) DSM-III R: Diagnostic and statistical manual of mental disorders
(1987)- et al.
Body—image aberration in schizophrenia
Journal of Abnormal Psychology
(1978) Single indicator of risk for schizophrenia: probable fact or likely myth?
Schizophrenia Bulletin
(1994)- et al.
The Temperament and Character Inventory (TCI): A guide to its development and use
(1994) Symptom Checklist-90-R (SCL-90-R)
(1993)- et al.
Standardization of the symptom check-list-90-R rating scale in a Greek population
Psychiatriki
(1991) - et al.
Correlation coefficients measured on the same individuals
Journal of the American Statistical Association
(1969)