A mood disorder, also known as an affective disorder, is any of a group of conditions of mental and behavioral disorder where the main underlying characteristic is a disturbance in the person's mood. The classification is in the Diagnostic and Statistical Manual of Mental Disorders (DSM) and International Classification of Diseases (ICD).
Mood disorders fall into seven groups, including: 1. abnormally elevated mood, such as mania or hypomania; 2. depressed mood, of which the best-known and most researched is major depressive disorder (MDD) (alternatively known as clinical depression, unipolar depression, or major depression); and 3. moods which cycle between mania and depression, known as bipolar disorder (BD) (formerly known as manic depression). 4. There are several subtypes of depressive disorders or psychiatric syndromes featuring less severe symptoms such as dysthymic disorder (similar to MDD, but longer lasting and more persistent, though often milder) and cyclothymic disorder (similar to but milder than BD).