Types of Depression. Depression occurs in several forms, and some of these may overlap. In the case of depression, psychiatrists may give more than one diagnosis because the illness is often linked with other problems like substance abuse, eating disorders or anxiety disorders. Clinical depression refers to a condition serious enough to require professional treatment. A person who experiences severe depression during a single period is said to have had an episode of clinical depression.
Major depression is marked by more severe or exaggerated symptoms.
When a person exhibits depressive symptoms, however mild, on a consistent basis, that person likely suffers from a dysthymic disorder. When a major depressive episode strikes someone with dysthymia, it is called double depression. Another severe type of depression is manic-depression, or bipolar disorder, so named because its sufferers experience not only the lows of depression but also the highs of mania. While research has led to a significant understanding of depression, scientists have not found the exact mechanism that triggers depression. Most likely there is no single cause.