Bipolar disorder, or manic-depressive illness, is a serious mood disorder that affects approximately 1 out of 100 people. The illness is typically identified by periods of depression marked by loss of energy, motivation, interest, ability to concentrate, and sadness that alternate with periods of mania characterized by intense speed or pressure of thought, speech, emotion and, at times, poor judgment. Bipolar disorder is caused by a combination of hereditary and environmental factors with persons having two first-degree relatives (for example, a brother and a mother with the illness) carrying a 40% lifetime risk of developing the illness themselves. Disruptions in the sleep-wake cycle such as shift work, jet lag, and all-night studying tend to precipitate episodes of mania. Additionally, there is seasonality at times to the illness with the peak months for psychiatric hospitalizations being in November and April when the length of the day is noticeably growing shorter or longer. The kindling hypothesis, as put forth by Robert M. Post, M.D. and others, suggests that brain areas (namely the amygdala and hippocampus) that connect energy and drive from the limbic system to higher association areas in the frontal cortex may be involved in causing the illness. When these structures connect too much energy from the limbic system, mania may result. Conversely, when these structures block limbic drive, a state of depressed mood could result. The hypothesis also suggests that brain chemicals normally released during periods of stress, such as endorphins and certain brain peptides, can worsen the illness over time, as can antidepressant medication. The hypothesis also predicts that medications that stabilize neuronal membranes in the limbic system should treat and/or prevent episodes of mania and depression. Such medications include anticonvulsants such as carbamazepine (Tegretol, Carbatrol) and valproic acid (Depakote). The treatment involves careful history taking of the number, duration, and severity of prior mood episodes, and the use of mood-stabilizing medications such as lithium, certain anticonvulsant medications, and some of the newer antipsychotic medications. Treatment often also includes supportive psychotherapy aimed at improving coping and organizational skills.