Cannabis use is associated with schizotypy and attentional disinhibition

While most neurochemical research into the pathogenesis of schizophrenia (SZ) has focused on the dopaminergic, glutamatergic, and serotonergic systems, the exact nature and cause of this disorder have proven intractable. Given the recent discovery and elucidation of the endogenous cannabinioid system, a re-examination of the cannabis-induced exacerbation hypothesis of SZ is warranted. The purpose of the present study was to assess whether current cannabis users exhibit personality correlates and neurocognitive deficits similar to those observed in SZ patients. 15 current cannabis users, 15 drug-free controls, and 10 past cannabis users were assessed on tasks which assess attentional inhibition, spatial working memory, olfactory identification, and schizotypal personality. Current cannabis users demonstrated deficits in attentional inhibition, decreased reaction time, and significantly higher scores on the schizotypal personality questionnaire (SPQ) compared with the non-using and past cannabis using groups. No group differences were found on the working memory or olfactory identification tasks. These results suggest that cannabis use can mimic attentional deficits seen in acute schizophrenia and is associated with schizotypal personality, thus setting the stage for a possible cannabinoid model of SZ.     

Handedness and schizotypy in non-clinical populations: influence of handedness measures and age on the relationship

This study aimed to evaluate the relation of handedness to schizotypal personality, with the influence of different handedness measures and age on the relationship investigated as well among representative samples of school students and community adults in Taiwan, where social pressure against certain left-handed actions was strong. In a total of 175 primary school students, 1020 junior high-school students, and 342 adult participants aged 20 to 65 years, all the participants completed the 12-item Annett handedness questionnaire, and the latter two groups further completed the Schizotypal Personality Questionnaire (SPQ) and the Perceptual Aberration Scale (PAS). There was a trend of increasing non-right handedness with younger age groups. Two classification methods in handedness, Annett's or Briggs-Nebes' three-category classification, led to very different frequency distribution and relation to schizotypy. For the adolescents, either Annett's classification or quantitative measures (Hand Preference Index and either-hand use scores) in handedness exhibited an association with schizotypy, whereas for the adults the either-hand use score was the only measure that did so. In contrast, no such difference was found using the Briggs-Nebes' classification method. The association of the non-right or mixed handedness was more consistent and of greater magnitude with the positive aspect of schizotypy, especially the PAS and the Cognitive-perceptual Dysfunction of the SPQ. The results highlight the potential of adolescents for future investigation on certain common causes underlying atypical cerebral lateralisation and positive schizotypy.     

Handedness and schizotypy in non-clinical populations: Influence of handedness measures and age on the relationship

This study aimed to evaluate the relation of handedness to schizotypal personality, with the influence of different handedness measures and age on the relationship investigated as well among representative samples of school students and community adults in Taiwan, where social pressure against certain left-handed actions was strong. In a total of 175 primary school students, 1020 junior high-school students, and 342 adult participants aged 20 to 65 years, all the participants completed the 12-item Annett handedness questionnaire, and the latter two groups further completed the Schizotypal Personality Questionnaire (SPQ) and the Perceptual Aberration Scale (PAS). There was a trend of increasing non-right handedness with younger age groups. Two classification methods in handedness, Annett's or Briggs-Nebes’ three-category classification, led to very different frequency distribution and relation to schizotypy. For the adolescents, either Annett's classification or quantitative measures (Hand Preference Index and either-hand use scores) in handedness exhibited an association with schizotypy, whereas for the adults the either-hand use score was the only measure that did so. In contrast, no such difference was found using the Briggs-Nebes’ classification method. The association of the non-right or mixed handedness was more consistent and of greater magnitude with the positive aspect of schizotypy, especially the PAS and the Cognitive-perceptual Dysfunction of the SPQ. The results highlight the potential of adolescents for future investigation on certain common causes underlying atypical cerebral lateralisation and positive schizotypy.     

Relationship between cannabis use, schizotypal traits, and cognitive function in healthy subjects

This research examined the relationship between cannabis use and schizotypal features. A sample of cannabis users (n = 20) was compared with a matched control group (n = 20). All participants were male students of the University of Hamburg. Subjects completed the Perceptual Aberration Scale and the Schizotypal Personality Questionnaire. A Negative Priming procedure and the Trail Making Test were carried out. A urine sample was obtained from each subject. Cannabis users exceeded controls in schizotypy scores and showed impaired neuropsychological parameters. Only within the cannabis group schizotypy scores correlated with neuropsychological parameters. Furthermore, cannabis users reported more often high-risk factors than controls. These findings indicate that among cannabis users there is an increased number of subjects with schizotypal features; schizotypal subjects seem to be more likely to use cannabis than the general population. Therefore, cannabis use may be a vulnerability indicator for schizophrenia.     

The SPQ: a scale for the assessment of schizotypal personality based on DSM-III-R criteria.

Existing self-report measures of schizotypal personality assess only one to three of the nine traits of schizotypal personality disorder. This study describes the development of the Schizotypal Personality Questionnaire (SPQ), a self-report scale modeled on DSM-III-R criteria for schizotypal personality disorder and containing subscales for all nine schizotypal traits. Two samples of normal subjects (n = 302 and n = 195) were used to test replicability of findings. The SPQ was found to have high sampling validity, high internal reliability (0.91), test-retest reliability (0.82), convergent validity (0.59 to 0.81), discriminant validity, and criterion validity (0.63, 0.68), findings which were replicated across samples. Fifty-five percent of subjects scoring in the top 10 percent of SPQ scores had a clinical diagnosis of schizotypal personality disorder. Thus, the SPQ may be useful in screening for schizotypal personality disorder in the general population and also in researching the correlates of individual schizotypal traits.     

Relationships between season of birth, schizotypy, temperament, character and neurocognition in a non-clinical population

While schizophrenia has been associated with a slight excess of winter/early spring birth, it is unclear whether there is such an association in relation to schizotypal personality traits. Season of birth has also been reported to relate to temperament and character personality dimensions and cognitive functioning. Moreover, non-clinical schizotypy has been shown to be associated with mild cognitive impairment, although its precise nature is yet to be elucidated. Here we examined the relationships between season of birth, schizotypal traits, temperament and character, and cognitive function. Four hundred and fifty-one healthy adults completed the Schizotypal Personality Questionnaire (SPQ). The Temperament and Character Inventory (TCI) and a neuropsychological test battery consisting of full versions of the Wechsler Memory Scale-Revised and the Wechsler Adult Intelligence Scale-Revised, and the Wisconsin Card Sorting Test, were also administered to most of the participants. The total SPQ score of those born in winter was significantly higher than that of the remaining participants. Season of birth was not significantly associated with any of the TCI dimensions or cognitive test results. Significant but mild relationships between higher SPQ scores and lower scores on some aspects of IQ were observed. These results support the notion that schizotypy and schizophrenia are neurodevelopmental conditions on the same continuum.     

Cannabis and psychometrically-defined schizotypy: Use, problems and treatment considerations

Cannabis use is associated with onset of psychosis in individuals vulnerable for developing schizophrenia-spectrum disorders. The present study addressed three knowledge gaps pertaining to this issue: 1) clarifying the incidence of cannabis use in schizotypal individuals, 2) examining how cannabis use is related to psychosocial and physiological problems in schizotypy and interest in treatment, and 3) examining how cannabis use is associated with positive, negative and disorganization features of schizotypy. Scores from a measure of schizotypal traits were used to trichotomize 1665 young adults into schizotypy (top 5% of scorers), non-schizotypy (bottom 50% of scorers) and “unconventional” (scorers within the 50th to 85th percentile) groups. Nearly a quarter of the schizotypy group endorsed cannabis use at least weekly, a rate nearly two to four times that of the other groups. The schizotypy group also reported a much greater frequency of cannabis-related problems compared to the other groups. Despite this, interest in treatment for cannabis use in the schizotypy group was not elevated. Interestingly, 85% of individuals in the schizotypy group reported interest in psychological/psychiatric treatment more generally. Cannabis use was not associated with abnormal patterns of positive or disorganized schizotypy traits in the schizotypy group relative to the other groups. However, cannabis use was associated with lower severity of negative traits. Implications of these results are discussed.     

Functional near-infrared spectroscopy reveals altered hemispheric laterality in relation to schizotypy during verbal fluency task

Previous functional neuroimaging studies have demonstrated that patients with schizophrenia and those with schizotypal personality disorder (SPD) show reduced laterality, or relative right hemispheric dominance, during the performance of cognitive activation tasks; however, neuroimaging studies looking at non-clinical schizotypy have been few. We have recently reported that schizotypal traits at a non-clinical level are associated with right prefrontal dominance during a letter version of the verbal fluency task (VFT), but it is unknown whether such relationship between schizotypy and functional laterality would be observed across various cognitive tasks. Here we examined the relationships of schizotypal traits as measured by the Schizotypal Personality Questionnaire (SPQ) in healthy adults with hemispheric lateralization of prefrontal activation during letter and category VFTs, using near-infrared spectroscopy. Thirty-two participants were divided into high- (n = 16) and low- (n = 16) SPQ groups by the median split of the total SPQ score. The high-SPQ group, but not low-SPQ group, showed significantly right-greater-than-left asymmetry of prefrontal activation during letter VFT, whereas such pronounced hemispheric asymmetry in relation to schizotypy was not found during category VFT. These results indicate that non-clinical schizotypy is related to right prefrontal preference during the letter version of VFT in particular, suggesting that the association between schizotypal traits and functional laterality may vary depending on cognitive activation tasks.     

精神分裂症患者一级亲属人格特征的研究

目的 探讨精神分裂症患者一级亲属的人格特征.方法 采用分裂型人格问卷(SPQ)及三维人格问卷(TPQ)评定181例精神分裂症患者一级亲属(高危组)、321名正常对照个体(对照组)的人格特征.结果 高危组sPQ阴性分裂型人格维度评分[(9.80±7.05)分]高于对照组[(8.42±5.87)分],差异有统计学意义(P＜0.05).高危组在TPQ寻求新奇维度评分[(15.60±5.62)分]、奖赏依赖维度评分[(17.41 ±1.13)分]与对照组[(14.20±2.83)分,(18.22±3.26)分]的差异均有统计学意义(P均＜0.01).高危组的阴性分裂型人格维度分数与寻求新奇维度、奖赏依赖维度分数显著相关(r=0.17和-0.23).结论 精神分裂症患者一级亲属具有阴性分裂型维度、寻求新奇维度、奖赏依赖维度的人格特征.     

精神分裂症一级亲属情感表达与人格特征的相关性

目的:探讨精神分裂症一级亲属情感表达与人格特征的相关性。方法:对130例精神分裂症一级亲属与117例对照组采用坎伯威尔家庭问卷中文版(CFI-CV)和分裂型人格问卷(SPQ)进行评估,根据CFI-CV评分,将样本分为高情感表达组和低情感表达组,对样本的人格特征进行比较。结果:在精神分裂症一级亲属中高情感表达组SPQ阴性分裂型评分显著高于低情感表达组(t=2.634,P<0.01),其余各维度差异均无统计学意义(P>0.05);精神分裂症一级亲属中高情感表达组SPQ阴性分裂型评分显著高于对照组中高情感表达组(t=2.687,P<0.01),其余各维度差异均无统计学意义(P>0.05)。结论:精神分裂症健康一级亲属的情感表达与人格特征有极高的相关性。     

Association between cannabis use and schizotypal dimensions – A meta-analysis of cross-sectional studies

Cannabis consumption can cause abuse and dependence and increase risk of developing psychiatric and somatic disorders. Several literature reviews explored the link between cannabis consumption and schizophrenia but none summarized the rich literature on cannabis and psychometric schizotypy. The aim of our review is to synthesize data from studies that explored the association between cannabis consumption and schizoptypal dimensions. A systematic review of the literature and, when needed, contact with the authors, allowed us to gather data from 29 cross-sectional studies. We compared schizotypy scores between subjects that never used cannabis and subjects that used it at least once (“never vs. ever”) and between current users and subjects that do not use cannabis currently (“current vs. other”). We conducted separate analyses for total schizotypy score and each of the three classical schizotypal dimensions (positive, negative, disorganized). For all eight comparisons, the cannabis group (“ever” or “current”) had higher schizotypy scores. Differences were in the small or medium range and, with the exception of the negative score in the current vs. other comparison, statistically significant. Cannabis consumption is associated with increased schizotypal traits. More research, using different approaches (e.g. longitudinal studies) is needed to explore the cause of this association.     

Elevated levels of cognitive-perceptual deficits in individuals with a family history of schizophrenia spectrum disorders

This study finds that the relatives of schizophrenics have elevated scores on the cognitive-perceptual factor of the schizotypal personality questionnaire (SPQ), particularly for the 'unusual perceptual experiences' and 'ideas of reference' subscales. These results support recent findings by Kremen et al. (1998) and suggest that previous failures to demonstrate elevated scores on 'positive' symptoms of schizotypy may be a function of instrumentation.     

Increased psychophysiological arousal and orienting at ages 3 and 11 years in persistently schizotypal adults

Abnormalities of psychophysiological arousal and orienting are thought to predispose to schizophrenia, but there have been no prior studies of early psychophysiological functioning in "persistent schizotypals" who remain stably schizotypal across time. This study assessed skin conductance (SC) arousal and orienting at ages 3 and 11 years, electroencephalography (EEG) at age 11 years, and behavior problems at age 17 years in 52 individuals who were stably schizotypal from ages 17 to 23 years, and 104 normal controls. Schizotypy was assessed at age 17 with the Schizophrenism scale, and at age 23 with the Schizotypal Personality Questionnaire (SPQ). Schizotypals had significantly increased SC arousal and increased SC amplitudes to neutral and aversive stimuli at both ages 3 and 11, and also reduced slow-wave left hemisphere EEG power at the beginning of the Continuous Performance Task (CPT) at age 11. Group differences in SC were greater for aversive than neutral stimuli. Schizotypals also had higher age 17 behavior ratings on psychotic behavior, anxiety-withdrawal, and conduct disorder. Findings indicate that heightened SC arousal and orienting in early childhood is a significant risk factor for later schizotypal personality, support a left hemisphere overactivation hypothesis of schizotypy, and illustrate the potential value of a longitudinal definition of persistent schizotypy.     

Neuropsychological impairment associated with symptoms of schizotypy: role of depressive and paranoid symptoms

: Little is known about the role of depressive symptoms in cognitive impairment associated with schizotypy. We compared neuropsychological performance among people reporting high levels of both schizotypal symptomatology on the Schizotypal Personality Questionnaire (SPQ) and depressive symptoms on the Beck Depression Inventory-II (BDI-II), people with high SPQ and low BDI-II, and healthy controls (low SPQ and BDI-II). We hypothesized that the group with both depressive and schizotypal features would demonstrate the greatest impairment. However, that group demonstrated better verbal memory and cognitive set maintenance. Further examination revealed higher endorsement of paranoid/suspicious symptoms in the people with both depressive and schizotypal features. Results highlight the importance of distinguishing among subtype variations in schizotypal research.     

The relationship between cannabis use and schizotypal symptoms.

To test the relationship between schizotypal symptoms and cannabis use in a non-clinical population, cannabis users and non-users were asked to complete the Schizotypal Personality Questionnaire. Significant differences in scores between the groups were observed. There may be a developmental process in the relationship between cannabis use and schizotypal symptoms.     

Multiple dimensions of schizotypy in first degree biological relatives of schizophrenia patients

Considerable research has been devoted to identifying individuals predisposed to schizophrenia, with much of the effort devoted to identifying the personality characteristics of the biological relatives of schizophrenia patients. Although resource-consuming interviews have yielded promising results, investigators have long sought self-report measures that index genetic risk for schizophrenia. The Schizotypal Personality Questionnaire (SPQ) is a self-report measure that assesses the nine features of DSM-defined schizotypy. The SPQ, modified to include validity scales, was administered to 135 nonpsychotic first degree relatives of schizophrenia patients and 112 healthy controls. Principal components analysis (PCA) yielded three factors that correlated highly with previously reported factors (social-interpersonal, cognitive-perceptual, and disorganization). Social-interpersonal deficits were found to best differentiate relatives from controls. Contrary to the hypothesis that schizophrenia relatives are more defensive in responding to schizotypy questionnaires, relatives were significantly less defensive than controls. The results demonstrate that a multidimensional paper-and-pencil measure can characterize schizotypal features in schizophrenia relatives, which will be useful for the further delineation of the heritable schizophrenia spectrum phenotype.     

Schizotypal traits and cognitive function in healthy adults

Growing evidence has shown that psychometrically identified schizotypes among student populations have subtle cognitive impairments in several domains such as attention, working memory and executive function, but the possible association between psychometric schizotypy in adult populations and cognitive function has not been well documented. Here we examined the association between schizotypal traits as assessed by the Schizotypal Personality Questionnaire (SPQ) and cognitive function including memory, attention, executive function, and general intelligence in 124 healthy adults. Cognitive functioning was assessed with the Wechsler Memory Scale-Revised (WMS-R), the Wechsler Adult Intelligence Scale-Revised (WAIS-R), and the Wisconsin Card Sorting Test (WCST). SPQ scores showed a significant inverse correlation with verbal IQ and the information, comprehension and similarities subtests. No correlation was found between SPQ scores and memory, attention, performance IQ, or executive functioning. These results indicate that schizotypal traits in healthy adults are associated with verbal IQ decrements, suggesting that schizotypal traits themselves, even at a non-clinical level, may play unfavorable roles in cognitive functioning, which is in line with the viewpoint that schizotypy is on a continuum with normality, with its extreme form being clinically expressed as schizophrenia.     

Positive and negative schizotypy in a student sample: neurocognitive and clinical correlates

Positive and negative schizotypy may represent discrete factors or dimensions. To determine if distinct neurocognitive profiles are associated with these dimensions or factors, we classified university students on the basis of positive and negative schizotypal symptoms and conducted separate analyses. Following prior work in the neuropsychiatric literature, we predicted that subtle prefrontal deficits would be selectively associated with negative schizotypal personality features in a nonclinical student sample. We also investigated the relationship between positive/negative schizotypy and associated clinical states or personality dimensions including antisocial personality disorder, obsessive-compulsive personality traits, generalized and social anxiety, empathy, and impulsivity. Classification of subjects into positive and negative schizotypy groups revealed distinct neurocognitive and clinical profiles. We observed a positive relation between measures of temporolimbic dysfunction, impulsivity, antisocial behavior, and positive schizotypal phenomena. Negative schizotypy was associated with subtle performance deficits on measures of frontal executive function, increased social anxiety, and obsessive-compulsive phenomena. Findings are consistent with the contention that positive and negative schizotypy represent discrete factors.     

The contribution of temperament and character to schizotypy multidimensionality

Schizotypy could be viewed either as an underlying "personality organization" that includes the "liability" to schizophrenia, i.e., as a hypothetical latent construct, or it could be referred to the phenotypic manifestations of a particular personality organization. The psychobiologic model of the structure of personality accounts for dimensions of both temperament and character. This study examined the covariances between Temperament and Character Inventory (TCI) scores and aspects of Schizotypal Personality Questionnaire (SPQ) scores in a nonclinical sample. The results showed the relationship between the number of schizotypal phenotypic traits, as quantified by SPQ measures, and a specific configuration of character, namely, high self-transcendence (ST), low self-directedness (SD), and low cooperativeness (C). Data suggested that the unique combination of high ST, low SD, and low C seems to lead to a special risk for schizotypy. In particular, ST is a predictor either of psychosis proneness or mature, effective adapted and self-satisfied personalities, depending on its interaction with other TCI dimensions, both temperament and character.     

Hedonic capacity and schizotypy: Evidence for the criterion validity of the ACIPS

The association between trait hedonic capacity and schizotypal personality traits was examined in a two studies of independent nonclinical samples. In both investigations, hedonic capacity was measured using the 17-item Anticipatory and Consummatory Interpersonal Pleasure Scale (ACIPS). In Study One, the young adults' (n = 1345) ACIPS scores were inversely associated with their scores on the Schizotypal Personality Questionnaire (SPQ). In Study Two, two groups of individuals identified on the basis of their scores on the Schizotypal Personality Questionnaire Brief-Revised (SPQ-BR) were compared in terms of their ACIPS responses and response patterns. Our results indicate that the high schizotypal subjects (n =38) and the low schizotypal subjects (n = 37) differed significantly in terms of their mean ACIPS scores, but not in terms of their mean reaction times. Despite differences in study design, both investigations indicated an association between the No Close Friends subscale of the SPQ and the ACIPS total score. These findings are considered in the context of other extant studies of schizotypal traits and the role of anhedonia in schizotypy. Overall, the findings provide further evidence for the criterion validity of the ACIPS.