In MDD, an increased number of AVP-expressing neurons and increased AVP mRNA expression has been reported in the hypothalamic Periventricular Nucleus (PVN) (84, 85), along with elevated AVP plasma levels (86–90), confirming vasopressinergic hyperactivity with pituitary but also extra-hypothalamic and extra-pituitary AVP neuropeptidergic hyperdrive (40, 91). The gene discussed is AVP; the disease is major depressive disorder.