MTNR1A and depressive disorder: In a study that investigated the effects of genetic deletion of the MT1 and/or MT2 receptors on depression- and anxiety-like behaviors in C3H/HeN mice, MT1 and/or MT2 receptor deletion reportedly caused a deficit in hedonic and social interaction behavior and increased anxiety-like behavior; the authors suggested that MT1 and/or MT2 melatonin receptor dysregulations were involved in depression and anxiety pathophysiology [264].