SST and major depressive disorder: Contrary to our prediction based on increased MDD prevalence in women, regardless of gonadal and adult hormonal status, FCG XY mice (i.e., genetic males that lack the sex-determining gene Sry on the Y chromosome; see 'Methods’) had lower expression of these three genes compared to XX mice, with concomitant elevated anxiety-like behavior; interestingly, adult testosterone treatment decreased anxiety-like behaviors, but did not affect Sst, Gad67, or Gad65 gene expression [13].