Male siblings with schizophrenia share alleles at the androgen receptor above chance expectation.

In families that included two or more siblings with schizophrenia or schizo-affective disorder male-male pairs were found to share alleles at the androgen receptor (AR) gene (in Xq11.2-q12) above chance expectation (p < 0.003); female-female and mixed sex pairs showed no such tendency. The findings are compatible with X-Y linkage or with an X-linked contribution to liability in males.