Sex differences of some kind—in prevalence, age at onset or presentation—have been demonstrated for a large portion of major psychiatric disorders. These may be due to some combination of artifact, differential susceptibility to environmental insults in males and females, effects of sex chromosome composition or differential nature and impact of genetic effects in males and females. Genetic epidemiologic studies have identified differences in heritabilities of several disorders between males and females and have provided support for a higher burden of genetic risk in the less affected sex in some cases. Molecular genetic studies have showed different SNPs associated with a disorder in males and females or differing strengths of SNP effects in males and females, and have also provided support for differing heritabilities or burden of risk alleles by sex. However, no consistent patterns have emerged across disorders and for the most part the mechanisms underlying sex differences in psychiatric disorders remain unexplained.
