The role of genetic factors in sex differences in a trait or disorder will differ according to the genetic architecture of the condition. Based on our current understanding, we anticipate that most common psychiatric disorders are polygenic and reflect the combined contributions of hundreds or thousands of genes 43 with a small subset of individuals having rare variants of larger effect, such as Fragile X in ASD or chromosome 22q11 deletion in schizophrenia. Genetic factors may contribute to sex differences either through the systematic differences between males and females in sex chromosome composition or through genotype‐by‐sex interactions resulting in differential impact of identical autosomal genetic variants in males and females.
