The structure of schizotypal personality traits: a cross-national study.

BACKGROUND: Schizotypal traits are considered a phenotypic-indicator of schizotypy, a latent personality organization reflecting a putative liability for psychosis. To date, no previous study has examined the comparability of factorial structures across samples originating from different countries and cultures. The main goal was to evaluate the factorial structure and reliability of the Schizotypal Personality Questionnaire (SPQ) scores by amalgamating data from studies conducted in 12 countries and across 21 sites. METHOD: The overall sample consisted of 27 001 participants (37.5% males, n = 4251 drawn from the general population). The mean age was 22.12 years (s.d. = 6.28, range 16-55 years). The SPQ was used. Confirmatory factor analysis (CFA) and Multilevel CFA (ML-CFA) were used to evaluate the factor structure underlying the SPQ scores. RESULTS: At the SPQ item level, the nine factor and second-order factor models showed adequate goodness-of-fit. At the SPQ subscale level, three- and four-factor models displayed better goodness-of-fit indices than other CFA models. ML-CFA showed that the intraclass correlation coefficients values were lower than 0.106. The three-factor model showed adequate goodness of fit indices in multilevel analysis. The ordinal α coefficients were high, ranging from 0.73 to 0.94 across individual samples, and from 0.84 to 0.91 for the combined sample. CONCLUSIONS: The results are consistent with the conceptual notion that schizotypal personality is a multifaceted construct and support the validity and utility of SPQ in cross-cultural research. We discuss theoretical and clinical implications of our results for diagnostic systems, psychosis models and cross-national mental health strategies.

Cognitive and oculomotor performance in subjects with low and high schizotypy: implications for translational drug development studies.

The development of drugs to improve cognition in patients with schizophrenia is a major unmet clinical need. A number of promising compounds failed in recent clinical trials, a pattern linked to poor translation between preclinical and clinical stages of drug development. Seeking proof of efficacy in early Phase 1 studies in surrogate patient populations (for example, high schizotypy individuals where subtle cognitive impairment is present) has been suggested as a strategy to reduce attrition in the later stages of drug development. However, there is little agreement regarding the pattern of distribution of schizotypal features in the general population, creating uncertainty regarding the optimal control group that should be included in prospective trials. We aimed to address this question by comparing the performance of groups derived from the general population with low, average and high schizotypy scores over a range of cognitive and oculomotor tasks. We found that tasks dependent on frontal inhibitory mechanisms (N-Back working memory and anti-saccade oculomotor tasks), as well as a smooth-pursuit oculomotor task were sensitive to differences in the schizotypy phenotype. In these tasks the cognitive performance of 'low schizotypes' was significantly different from 'high schizotypes' with 'average schizotypes' having an intermediate performance. These results indicate that for evaluating putative cognition enhancers for treating schizophrenia in early-drug development studies the maximum schizotypy effect would be achieved using a design that compares low and high schizotypes.

Behavioral and fMRI evidence of the differing cognitive load of domain-specific assessments.

Standards-referenced educational reform has increased the prevalence of standardized testing; however, whether these tests accurately measure students' competencies has been questioned. This may be due to domain-specific assessments placing a differing domain-general cognitive load on test-takers. To investigate this possibility, functional magnetic resonance imaging (fMRI) was used to identify and quantify the neural correlates of performance on current, international standardized methods of spelling assessment. Out-of-scanner testing was used to further examine differences in assessment results. Results provide converging evidence that: (a) the spelling assessments differed in the cognitive load placed on test-takers; (b) performance decreased with increasing cognitive load of the assessment; and (c) brain regions associated with working memory were more highly activated during performance of assessments that were higher in cognitive load. These findings suggest that assessment design should optimize the cognitive load placed on test-takers, to ensure students' results are an accurate reflection of their true levels of competency.

Affective instability prior to and after thoughts about self-injury in individuals with and at-risk of psychosis: a mobile phone based study.

It has been proposed that affective instability may be associated with thoughts about self-injury. The aim of this study was to test the hypotheses that instability in feelings of depression, but not anxiety, guilt, or hostility, would predict greater concurrent and subsequent thoughts about self-injury. Thirty-six individuals with psychosis completed questions on touch-screen mobile phones at semi-random times each day for one week. The instability of depression predicted greater concurrent and subsequent levels of thoughts about self-injury, even when controlling for depression level. Conversely, self-injurious thoughts predicted more stable depression. The instability of guilt, anxiety, and hostility did not significantly predict levels of thoughts about self-injury. Results indicate that a variable depressive state may trigger the onset of thoughts about self-injury, which increases the risk of its subsequent recurrence. The onset of self-injurious thoughts may, however, have a stabilizing effect on subsequent depression.

Dissociation mediates the relationship between childhood trauma and hallucination-proneness.

BACKGROUND: It has been proposed that the relationship between childhood trauma and hallucinations can be explained by dissociative processes. The present study examined whether the effect of childhood trauma on hallucination-proneness is mediated by dissociative tendencies. In addition, the influence of dissociative symptoms on a cognitive process believed to underlie hallucinatory experiences (i.e. reality discrimination; the capacity to discriminate between internal and external cognitive events) was also investigated. METHOD: Patients with schizophrenia spectrum disorders (n=45) and healthy controls (with no history of hallucinations; n=20) completed questionnaire measures of hallucination-proneness, dissociative tendencies and childhood trauma, as well as performing an auditory signal detection task. RESULTS: Compared to both healthy and non-hallucinating clinical controls, hallucinating patients reported both significantly higher dissociative tendencies and childhood sexual abuse. Dissociation positively mediated the effect of childhood trauma on hallucination-proneness. This mediational role was particularly robust for sexual abuse over other types of trauma. Signal detection abnormalities were evident in hallucinating patients and patients with a history of hallucinations, but were not associated with pathological dissociative symptoms. CONCLUSIONS: These results are consistent with dissociative accounts of the trauma-hallucinations link. Dissociation, however, does not affect reality discrimination. Future research should examine whether other cognitive processes associated with both dissociative states and hallucinations (e.g. deficits in cognitive inhibition) may explain the relationship between dissociation and hallucinatory experiences.

Experience sampling research in individuals with mental illness: reflections and guidance.

OBJECTIVE: The experience sampling method (ESM) represents a valuable way of assessing clinical phenomena in real world settings and across time. Despite its theoretical advantages, using this methodology in psychiatric populations is challenging. This paper acts as a guide to researchers wishing to employ this approach when investigating mental illness. METHOD: The contents represent the opinions of researchers around the United Kingdom and the Netherlands who are experienced at using the ESM. RESULTS: In ESM studies, participants are required to fill in questions about their current thoughts, feelings and experiences when prompted by an electronic device (e.g. a wristwatch, PDA). Entries are typically made at fixed or random intervals over 6 days. This article outlines how to design and validate an ESM diary. We then discuss which sampling procedure to use and how to increase compliance through effective briefing and telephone sessions. Debriefing, data management and analytical issues are considered, before suggestions for future clinical uses of the ESM are made. CONCLUSION: The last decade has seen an increase in the number of studies employing the ESM in clinical research. Further research is needed to examine the optimal equipment and procedure for different clinical groups.

Cannabis-induced psychotic-like experiences are predicted by high schizotypy. Confirmation of preliminary results in a large cohort.

BACKGROUND: Cannabis use has been identified as a possible risk factor for developing schizophrenia. In a previous paper we reported preliminary evidence that cannabis use increases the likelihood of psychosis-like experiences in non-clinical respondents who scored highly on a measure of schizotypy. We now present findings from pooled data from 3 new follow-up studies comprising a sample of 477 respondents, of whom 332 reported using cannabis at least once. SAMPLING AND METHODS: As in our previous study, the psychological effects of cannabis were assessed with the Cannabis Experiences Questionnaire, from which 3 subscales can be derived; encompassing pleasurable experiences, psychosis-like experiences and after-effects. The respondents also completed the brief Schizotypal Personality Questionnaire. RESULTS: Cannabis use was reported by 70% of the sample. Use per se was not significantly related to schizotypy. However, high scoring schizotypes were more likely to report both psychosis-like experiences and unpleasant after-effects associated with cannabis use. The pleasurable effects of cannabis use were not related to schizotypy. Exploratory factor analysis of the pooled data from this study and our previous report (providing a sample of >400 cannabis users) suggested a 3-factor solution. These were characterised as a psychotic-dysphoric index (factor 1), an expansive index (factor 2) and an intoxicated index (factor 3). Schizotypy was highly correlated with factors 1 and 3, though not with factor 2. CONCLUSION: High scoring schizotypes who use cannabis are more likely to experience psychotic-dysphoric phenomena and intoxicating effects during and after use. Our results confirm and expand the findings reported in our previous study. They are consistent with the hypothesis that cannabis use may be a risk factor for full psychosis in this group.

Schizotypy and psychosis-like experiences from recreational cannabis in a non-clinical sample.

BACKGROUND: The relationship between cannabis use and psychosis is still a matter for debate. Accounting for the individual differences in subjective experiences to recreational cannabis use in the general population may hold some clues to the aetiological relationship between cannabis and psychotic symptoms. We hypothesized that schizotypy would account for the individual differences in subjective experiences after cannabis use but not in patterns of use. METHOD: In a sample of 532 young people who had used cannabis at least once, we examined the relationship between the Cannabis Experiences Questionnaire (CEQ) and the Schizotypal Personality Questionnaire (SPQ). Additionally, we examined the psychometric properties of the CEQ. RESULTS: We replicated our previously reported findings that schizotypy was associated with increased psychosis-like experiences and after-effects, but also found that high-scoring schizotypes reported more pleasurable experiences when smoking cannabis. Using new subscales derived from principal components analysis (PCA), we found that the psychosis-like items were most related to varying rates of schizotypy both during the immediate use of cannabis and in the after-effects of cannabis use. High-scoring schizotypes who used cannabis experienced more psychosis-like symptoms during and after use. CONCLUSIONS: Our results suggest that cannabis use may reveal an underlying vulnerability to psychosis in those with high schizotypal traits.

Cannabis-induced psychosis-like experiences are associated with high schizotypy.

OBJECTIVE: Recent studies have suggested that cannabis use is a risk factor for developing schizophrenia. We tested the hypothesis that cannabis use increases the likelihood of psychosis-like experiences in non-clinical participants who scored highly on a measure of schizotypy. METHOD: The psychological effects of cannabis were assessed in 137 healthy individuals (76% female, mean age 22 years) using a newly developed questionnaire concerned with subjective experiences of the drug: the Cannabis Experiences Questionnaire. The questionnaire has three subscales: Pleasurable Experiences, Psychosis-Like Experiences and After-Effects. Respondents also completed the brief Schizotypal Personality Questionnaire. RESULTS: Cannabis use was reported by 72% of the sample. Use per se was not significantly related to schizotypy. However, high scoring schizotypes were more likely to report both psychosis-like experiences and unpleasant after-effects associated with cannabis use. The pleasurable effects of cannabis use were not related to schizotypy score. CONCLUSION: High scoring schizotypes who use cannabis are more likely to experience psychosis-like phenomena at the time of use, and unpleasant after-effects. Our results are consistent with the hypothesis that cannabis use is a risk factor for full psychosis in this group.