Moreover, since the possible sex difference in the expression of SCN AVP-ir in depression was not investigated in one of our group’s previous studies (Zhou et al. 2001), we re-analyzed those data and confirmed the presence of a significantly increased number of AVP-expressing neurons only in females [female control 3422 (1945–4298); female depression 7947 (6362–11,070), P = 0.029], while only a trend of increase was present in the male depression group [male control 3534 (2467–6098); male depression 6178 (3832–7276), P = 0.073]. This evidence concerns the gene AVP and major depressive disorder.