Clinically significant non-major depression: old concepts, new insights.

Clinically significant non-major depression has been underinvestigated despite its high prevalence and public health impact. Although there is an increasing recognition of the importance of non-major forms of depression, their nosological boundaries and neurobiological mechanisms remain largely unknown. The authors discuss the literature pertaining to the current concepts, phenomenology, neurobiology, and treatment approaches to geriatric non-major clinically significant depression. They examine the similarities and differences between various subtypes of depressive disorders and compare non-major, clinically significant depression in elderly patients with non-geriatric adult populations. They draw conclusions from the published literature and propose clinical criteria for the diagnosis of clinically significant non-major depression in elderly persons.