Depression epidemiology and its treatment evolution.

Approximately 1 in 5 US adults have at least one episode of major depression in their lifetime. Of those who do, the majority will relapse over the long term and many will have psychosocial disabilities and reduced functioning. Over the past century, a range of medications have been developed to treat depression, although some effective medications have been superseded by newer treatments with an improved safety and tolerability profile. A reconsideration of some older medications is warranted until agents with truly novel mechanisms of action and good safety and tolerability profiles are available.