A mood stabilizer is a psychiatric medication used to treat mood disorders characterized by intense and sustained mood shifts, which is not the same as "feeling good one minute and then bad the next." The most common is bipolar disorder, where mood stabilizers suppress swings between mania and depression, and these drugs are also used in borderline personality disorder. Most mood stabilizers are anticonvulsants, with the important exception of lithium, which is the oldest and best known mood stabilizing drug.
Most mood stabilizers are purely antimanic agents, meaning that they are effective at treating mania and mood cycling and shifting, but are not effective at treating depression. The principal exceptions to that rule, because they treat both manic and depressive symptoms, are lamotrigine and lithium carbonate. While an antimanic agent such as valproic acid or carbamazepine cannot treat depression directly as the former two drugs can, it is widely thought to help ward off depression in bipolar patients by keeping them out of mania and thus preventing their moods from cycling.
Nevertheless, an antidepressant is often prescribed in addition to the mood stabilizer during depressive phases. This brings some risks, however, as antidepressants can induce mania, psychosis, and other disturbing problems in bipolar patients -- particularly when taken alone, but sometimes even when used with a mood stabilizer. It should be noted that antidepressants' utility in treating depression-phase bipolar disorder is unclear.
Drugs commonly classed as mood stabilizers include:
Sometimes mood stabilizers are used in combination, such as lithium with one of the anticonvulsants.
Many atypical antipsychotics also have mood stabilizing effects and are thus commonly prescribed even when psychotic symptoms are absent. It is also conjectured that Omega-3 fatty acids may have a mood stabilizing effect. However, more research is needed to verify this (a multi-year study of this is now being carried out as of 2001).
One possible downstream target of several mood stabilizers such as lithium, valproate and carbamazepine is arachidonic acid cascade.