Interaction Effects of Season of Birth and Cytokine Genes on Schizotypal Traits in the General Population

Environmental Risk Factors for Schizophrenia and Bipolar Disorder and Their Relationship to Genetic Risk: Current Knowledge and Future Directions

Schizophrenia (SZ) and bipolar disorder (BD) are severe psychiatric disorders which result from complex interplay between genetic and environmental factors. It is well-established that they are highly heritable disorders, and considerable progress has been made identifying their shared and distinct genetic risk factors. However, the 15-40% of risk that is derived from environmental sources is less definitively known. Environmental factors that have been repeatedly investigated and often associated with SZ include: obstetric complications, infections, winter or spring birth, migration, urban living, childhood adversity, and cannabis use. There is evidence that childhood adversity and some types of infections are also associated with BD. Evidence for other risk factors in BD is weaker due to fewer studies and often smaller sample sizes. Relatively few environmental exposures have ever been examined for SZ or BD, and additional ones likely remain to be discovered. A complete picture of how genetic and environmental risk factors confer risk for these disorders requires an understanding of how they interact. Early gene-by-environment interaction studies for both SZ and BD often involved candidate genes and were underpowered. Larger samples with genome-wide data and polygenic risk scores now offer enhanced prospects to reveal genetic interactions with environmental exposures that contribute to risk for these disorders. Overall, although some environmental risk factors have been identified for SZ, few have been for BD, and the extent to which these account for the total risk from environmental sources remains unknown. For both disorders, interactions between genetic and environmental risk factors are also not well understood and merit further investigation. Questions remain regarding the mechanisms by which risk factors exert their effects, and the ways in which environmental factors differ by sex. Concurrent investigations of environmental and genetic risk factors in SZ and BD are needed as we work toward a more comprehensive understanding of the ways in which these disorders arise.

The Association Between Season of Birth and Atopic Dermatitis in the Northern Hemisphere: A Systematic Review and Meta-Analysis

BACKGROUND

Cold and dry climate negatively affects skin barrier functions. This could explain the higher incidence of atopic dermatitis (AD) in Northern countries distant from the equator, as well as the general worsening of AD in Northern European winter months. Although it has been suggested that fall and winter birth is associated with AD, this remains unknown.

OBJECTIVES

To examine whether the prevalence of AD is associated with season of birth.

METHODS

We conducted a systematic review and meta-analysis. Two reviewers independently searched 3 databases. Study quality was assessed using a Newcastle-Ottawa scale. Study heterogeneity was assessed with Cochrane Q and I² statistics. Odds ratios with 95% CIs were calculated. Publication bias was assessed using funnel plots.

RESULTS

The systematic review identified 23 relevant articles of which 9 articles were included in the meta-analysis. Among a total of 726,378 children aged 0 to 12 years, the overall pooled prevalence of AD was 12.9%. The pooled prevalence of AD was 15.4% (95% CI, 12.1%-19.1%), 14.9% (95% CI, 12.0%-18.1%), 12.7% (95% CI, 10.2%-15.4%), and 13.7% (95% CI, 10.8%-17.0%), among children born in the fall, winter, spring, and summer, respectively. AD was significantly associated with fall (odds ratio, 1.16; 95% CI, 1.06-1.28; P = .0018) and winter (odds ratio, 1.15; 95% CI, 1.04-1.27; P = .0076) birth compared with spring birth.

CONCLUSIONS

Although a positive and significant association was observed between being born in fall and winter and developing AD on the Northern hemisphere, there is a need for additional and better-designed studies to understand the effect of seasonal changes on the risk of AD.

Opening up new horizons for psychiatric genetics in the Russian Federation: moving toward a national consortium

We provide an overview of the recent achievements in psychiatric genetics research in the Russian Federation and present genotype-phenotype, population, epigenetic, cytogenetic, functional, ENIGMA, and pharmacogenetic studies, with an emphasis on genome-wide association studies. The genetic backgrounds of mental illnesses in the polyethnic and multicultural population of the Russian Federation are still understudied. Furthermore, genetic, genomic, and pharmacogenetic data from the Russian Federation are not adequately represented in the international scientific literature, are currently not available for meta-analyses and have never been compared with data from other populations. Most of these problems cannot be solved by individual centers working in isolation but warrant a truly collaborative effort that brings together all the major psychiatric genetic research centers in the Russian Federation in a national consortium. For this reason, we have established the Russian National Consortium for Psychiatric Genetics (RNCPG) with the aim to strengthen the power and rigor of psychiatric genetics research in the Russian Federation and enhance the international compatibility of this research.The consortium is set up as an open organization that will facilitate collaborations on complex biomedical research projects in human mental health in the Russian Federation and abroad. These projects will include genotyping, sequencing, transcriptome and epigenome analysis, metabolomics, and a wide array of other state-of-the-art analyses. Here, we discuss the challenges we face and the approaches we will take to unlock the huge potential that the Russian Federation holds for the worldwide psychiatric genetics community.