Mood disorders are total body disorders that affect how people think, behave, care for themselves, and their overall health. There are three main types of mood disorders: depression, dysthymia, and bipolar disorder. Depression is characterized by feelings of sadness, loss of interest, changes in appetite or sleep, fatigue, concentration problems, and thoughts of death or suicide for at least two weeks. Bipolar disorder involves alternating periods of depression and mania or hypomania. Dysthymia is a chronic mild depression lasting at least two years. Mood disorders can be triggered by life events but are disproportionately severe and long-lasting compared to typical sadness.