Schizophrenia-proneness, season of birth and sleep: Elevated schizotypy scores are associated with spring births and extremes of sleep

Season of birth and schizotypy in a sample of undergraduate students

PURPOSE

In line with the psychotic continuum theory, the study of psychometric schizotypy in non-clinical samples has been proposed as a convenient yet powerful method for studying the etiology of psychosis. Based on this paradigm, several studies explored the association between season of birth (SoB) and schizotypy but led to inconsistent results. Building on the analysis of the previous studies, in the present study, we aimed to advance our understanding by improving the methodology (using a homogeneous group, eliminating unreliable respondents, taking into account potential confounders) and the reporting.

METHODS

Subjects were recruited among undergraduate students from 3 Romanian Universities. To limit the potential influence of invalid response, we applied methods for detecting unreliable and/or biased questionnaires and excluded subjects with unreliable/ biased answers from the analyses. Schizotypal dimensions were measured using the Romanian translation of the 22-items Schizotypal Personality Questionnaire-Brief (SPQ-B). The association between schizotypy scores and season of birth was explored using linear regression.

RESULTS

In a sample of 484 undergraduate students from Romania, we found that being born in late winter/early spring (February and March) was associated to higher total schizotypy score and disorganization. Furthermore, we found that restricting the sample to subjects born in an urban environment increased the strength of the association.

CONCLUSION

This study is consistent with an association between SoB and the risk of psychotic disorders.

Schizotypy Moderates the Relationship Between Sleep Quality and Social Cognition

ABSTRACT

Poor sleep quality has been tied to worse social cognition. Social cognitive deficits have been noted in those with high schizotypy. Yet, no study has assessed whether schizotypy moderates the relationship between sleep quality and social cognition, which may be vital to our understanding of contributors to social functioning. We conducted a cross-sectional analysis of associations of sleep quality and social cognition, with potential moderation by schizotypy. Participants ( n = 906) completed self-report measures of schizotypy, sleep quality, and social cognition. Levels of schizotypy significantly moderated some of the relationships between sleep and social cognition. For participants low in total or interpersonal schizotypy, worse sleep quality was associated with worse theory of mind scores. For participants low in total, disorganized, or cognitive perceptual schizotypy, worse sleep quality was associated with worse self-reported cognitive empathy. For those high in these facets of schizotypy, worse sleep quality was associated with better self-reported cognitive empathy. These results suggest that the individual facets of schizotypy provide additional information and, therefore, are important to assess when examining social cognition and sleep.

Nutrition, Sleep, and Exercise as Healthy Behaviors in Schizotypy: A Scoping Review

This scoping review identifies the role of nutrition, sleep, and exercise as healthy behaviors in non-clinical individuals with schizotypy throughout the lifespan.

METHODS

We systematically reviewed the existing literature on these topics through databases including: PsycINFO, Scopus, APA PsycNet, ScienceDirect, Wiley Online Library, and SpringerLink.

RESULTS

Of the 59 studies found, a total of 29 studies met the inclusion criteria on the review topic. Included studies reflect varying study designs (cross-sectional, multiple time-point, intervention, randomized-placebo controlled trials), assessment of schizotypy and associated healthy behaviors, focus on various samples and lifespan (e.g., undergraduates, adolescents, at-risk individuals), and stem from different countries.

CONCLUSION

While a moderate number of studies address the role of nutrition, sleep, and physical exercise in relation to schizotypy, studies intersecting these topics are limited. Of the limited studies that do exist, the majority are correlational with the beginnings of causal support from intervention studies. As such, more research is needed on the topics of nutrition, sleep, and exercise in relation to schizotypy. Specifically, future research should focus on providing a more holistic understanding of schizotypal traits and its subtypes, and which specific or combination of behaviors may reduce levels of schizotypy.

Early life factors of schizotypal personality disorder in adolescents: A systematic review

WHAT IS KNOWN ON THE SUBJECT?: The complexity and high prevalence of schizotypal personality disorders (SPD) pose serious challenges for mental health practice in its management, and also bring severe consequences for the patients. The identification of the specific early life factors (ELFs) that confer risk to SPD has become a major focus of clinical research on schizophrenia-spectrum disorders which aligns well with the mental health nursing's responsibility in health promotion, prevention and treatment. WHAT THIS PAPER ADDS TO EXISTING KNOWLEDGE?: Adolescents may experience certain ELFs, which contribute to the occurrence of SPD, but no systematic review has been conducted to identify ELF among them. And nursing literature addressing modifiable ELF is very limited. Two clusters of ELF and SPD in adolescents were identified: prenatal and early postnatal factors; childhood trauma and parental factors. The findings also show that more research is needed to determine the specificity and cumulative effects of ELF on the development of SPD by using rigorous and comprehensive measurements and a longitudinal design. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: Mental health nurses, especially nurses in the primary care, should be aware of potentially modifiable ELFs and incorporate more comprehensive and valid instrument for assessing cumulative ELF and SPD. These findings may serve to inform possible future interventions for SPD, such as parent education and support to mitigate these risk factors.

ABSTRACT

INTRODUCTION: Schizotypal personality disorder (SPD) affects 4% of the general population in the United States. The identification of early life factors (ELFs) that confer risk to SPD in adolescents (ages 10-24 years old) has become a major focus of clinical research on schizophrenia-spectrum disorders.

AIM

This systematic review aims to determine what ELFs contribute to the onset of SPD in the adolescent population.

METHODS

A systematic search of PubMed, PsycINFO, Psychiatry online, Scopus, Web of Science, EMBASE and CINAHL databases was conducted using relevant keywords. Data were extracted using a standardized form following PRISMA guidelines.

RESULTS

Twenty-four studies met the criteria for inclusion. ELFs in the development of SPD were grouped into two important clusters: (a) prenatal and early postnatal factors; (b) childhood trauma and parental factors.

CONCLUSION

Mental health nurses, especially nurses in primary care, should be aware of potentially modifiable ELF. Longitudinal research is needed to determine the causative roles of these ELF play in the occurrence of SPD by using rigorous measurements.

IMPLICATIONS FOR PRACTICE

These findings call for awareness of the modifiable ELF for SPD and also inform possible future interventions to reduce these risks, such as parent-training or environmental enrichment programmes.

Long and short sleep duration and psychotic symptoms in adolescents: Findings from a cross-sectional survey of 15 786 Japanese students

Sleep problems during adolescence affect current and subsequent mental health and are associated with experiences of psychotic symptoms. Recent studies have suggested that short sleep duration increases the risk of experiencing psychotic symptoms in the general adolescent population; however, whether long sleep duration is associated with an increased risk of psychotic symptoms in adolescence remains unclear. The present study aimed to examine the relationships between long sleep duration, short sleep duration, and the risk of experiencing psychotic symptoms in adolescence. Cross-sectional survey data from 15,786 junior and senior high school students (12- to 15-year-olds and 15- to 18-year-olds, respectively) in Japan were collected and analyzed using logistic regression analysis after controlling for covariates, including depressive symptoms. Long sleep duration was associated with a 1.6- to 2.8-fold increased risk of psychotic symptoms in male but not in female adolescents. Short sleep duration was also related with a 1.6- to 2.9-fold increased risk of experiencing psychotic symptoms, except for 15- to 18-year-old female adolescents. The present study suggested that adolescents with long and short sleep duration should be assessed for their risk of experiencing psychotic symptoms regardless of concurrent depressive symptoms.

Season of birth and population schizotypy: Results from a large sample of the adult general population

Although the last years have seen an increasing interest in schizotypy and its pathogenesis, there exist only a handful of studies examining the possible interaction between season of birth (SOB) and schizotypic personality structure. Available research used differing screening instruments, rendering comparisons between studies difficult, and sample sizes in adult populations may have been too small to detect a mild effect. The current study examined the association between SOB and psychometric schizotypy in the so far single-largest sample from the adult general population (N=8114), balanced for men and women, and utilizing a valid and reliable instrument for the assessment of schizotypy. Using the 12 most informative items of the Schizotypal Personality Questionnaire Brief, we obtained evidence of a small, but significant, effect of late winter and early spring births (February/March) on psychometric schizotypy. The effect was not constrained to women, but affected men and women alike. The observed association between SOB and schizotypy appears compatible with seasonal variations of temperature and influenza prevalence, and with recent evidence on seasonal variability in the activity of the human immune system. Our findings lend support to the continuum hypothesis of schizotypy and schizophrenia, for which SOB effects have been previously established.

Season of birth and subclinical psychosis: systematic review and meta-analysis of new and existing data

Season of birth (SOB) has been shown to modify the risk of several health outcomes, including a number of neuropsychiatric disorders. Empirical evidence indicates that subclinical forms of psychosis in the general population share some risk factors with categorical diagnoses of psychosis. Hence, by systematically reviewing and meta-analyzing new and existing data, the current work aimed to determine whether there is evidence of an association between winter SOB and subclinical psychosis in the general population. Our meta-analytic results do not indicate an association between winter SOB and schizotypy in adult populations, although they indicate winter SOB may be a risk factor for psychotic experiences or symptoms in children around 12-15 years (OR=1.12, 95%CI:1.03-1.21). In the whole new dataset for adults (n=481, mean age=22.8 years) no association was detected in either an unadjusted model or adjusting for gender and age. Overall, our results indicate that the association between winter SOB and increased subclinical psychosis may hold in children, but does not in the broad general adult population. Nevertheless, the epidemiological and clinicopathological significance of winter SOB as a risk factor for subclinical psychosis would probably be slight due to the small effect sizes indicated by the reports available to date.

Prediction of individual season of birth using MRI

Previous research suggests statistical associations between season of birth (SOB) with prevalence of neurobehavioral disorders such as schizophrenia and bipolar disorder, personality traits such as novelty and sensation seeking, and suicidal behavior. These effects are thought to be mediated by seasonal differences in perinatal photoperiod, which was recently shown to imprint circadian clock neurons and behavior in rodents. However, it is unknown whether SOB is associated with any measurable differences in the normal human adult brain, and whether individual SOB can be deduced based on phenotype. Here I show that SOB predicts morphological differences in brain structure, and that MRI scans carry spatially distributed information allowing significantly above chance prediction of an individual's SOB. Using an open source database of over 550 structural brain scans, Voxel-Based Morphometry (VBM) analysis showed a significant SOB effect in the left superior temporal gyrus (STG) in males (p=0.009, FWE whole-brain corrected), with greater gray matter volumes in fall and winter births. A cosinor analysis revealed a significant annual periodicity in the left STG gray matter volume (Zero Amplitude Test: p<5×10(-7)), with a peak towards the end of December and a nadir towards the end of June, suggesting that perinatal photoperiod accounts for this SOB effect. Whole-brain VBM maps were used as input features to multivariate machine-learning based analyses to classify SOB. Significantly greater than chance prediction was achieved in females (overall accuracy 35%, p<0.001), but not in males (overall accuracy 26%, p=0.45). Pairwise binary classification in females revealed that the highest discrimination was obtained for winter vs. summer classification (peak area under the ROC curve=0.71, p<0.0005). Discriminating regions included fusiform and middle temporal gyrus, inferior and superior parietal lobe, cerebellum, and dorsolateral and dorsomedial prefrontal cortex. Results indicate that SOB is detectable with MRI, imply that SOB exerts effects on the developing human brain that persist through adulthood, and suggest that neuroimaging may be a valuable intermediate phenotype in bridging the gap between SOB and personality and neurobehavioral disorders.

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.

Birth characteristics and schizotypy: evidence of a potential "second hit"

Schizophrenia is associated with a modest increase in winter births as well as increased odds of being born in more densely populated and midrange latitude regions. It is unclear the degree to which these findings hold for individuals with schizotypy, defined in terms of the personality organization that is a potential precursor to schizophrenia-spectrum disorders. This issue is important for understanding whether birth factors contribute to general schizophrenia vulnerability or whether they reflect a secondary "hit" that increases the likelihood of psychosis onset in vulnerable individuals. The present project examined season of birth, birthplace population and birth location in a large group of young adults from the southeastern United States. Individuals with extreme schizotypy scores did not differ from those without schizotypy in season of birth, birthplace latitude or population. However, 60% of individuals within the schizotypy group who reported a diagnosis of schizophrenia or prior hospitalization were born during winter months; a dramatic difference from other individuals within the schizotypy group. We also found that individuals with negative/schizoid traits showed a birthplace population less than half that of other individuals with schizotypy. Season of birth appears to be a "second hit" that is related to expression of psychopathology onset in vulnerable individuals. This finding, and the unexpected inverse relationship between birthplace population and negative/schizoid traits, is discussed.