Adult brain neurogenesis and psychiatry: a novel theory of depression

Neurogenesis (the birth of new neurons) continues postnatally and into adul thood in the brains of many animal species, including humans. This is parti cularly prominent in the dentate gyrus of the hippocampal formation. One of the factors that potently suppresses adult neurogenesis is stress, probabl y due to increased glucocorticoid release. Complementing this, we have rece ntly found that increasing brain levels of serotonin enhance the basal rate of dentate gyrus neurogenesis. These and other data have led us to propose the following theory regarding clinical depression. Stress-induced decreas es in dentate gyrus neurogenesis are an important causal factor in precipit ating episodes of depression. Reciprocally, therapeutic interventions for d epression that increase serotonergic neurotransmission act at least in part by augmenting dentate gyrus neurogenesis and thereby promoting recovery fr om depression. Thus, we hypothesize that the waning and waxing of neurogene sis in the hippocampal formation are important causal factors, respectively , in the precipitation of, and recovery from, episodes of clinical depressi on.