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.
Fred K. Berger, MD, Addiction and Forensic Psychiatrist, Scripps Memorial Hospital, La Jolla, California. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.