With advances in the identification of polymorphic markers across the human genome, the case‐control study design has become increasingly popular in psychiatric genetics with sample sizes in some studies greater than 900 000 individuals. The Psychiatric Genomics Consortium (PGC, https://www.med.unc.edu/pgc/) has conducted genome‐wide meta‐ and mega‐analyses for multiple psychiatric disorders including ADHD, ASD, bipolar disorder, major depression and schizophrenia. Yet, sex differences in genetic architecture of these conditions has received relatively little attention. For example, the most recent GWAS that identified 102 variants associated with depression, controlled for sex as a potential confounding variable rather than examining its effect directly. 110 The CONVERGE Consortium study of recurrent depression was restricted to female participants; however, the replication had participants of both sexes. 111 Controlling for sex by including it as a covariate in GWAS is far more common than explicitly examining the effect of sex. In 2017, Powers and colleagues 112 reported that only 1% of genetic association studies of any disease had reported sex differences, and an even smaller proportion considered sex chromosomes.
