The starting point of this study has been the observation that a direct correlation exists between the levels of Dlx5/6 expression in GABAergic neurons and the severity of depressive-like behaviours in the mouse: when Dlx5/6 are deleted in these neurons, depressive-like behaviours are reduced whereas more severe signs of depression are observed when Dlx5 expression is experimentally increased in the same neurons. The gene discussed is DLX5; the disease is major depressive disorder.