Depression is defined as a mood disorder, and there are several subtypes. Bipolar disorder, also known as manic-depressive illness, is considered in a separate category.
Review Date 10/7/2018
Updated by: Ryan James Kimmel, MD, Medical Director of Hospital Psychiatry at the University of Washington Medical Center, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.