Vincent van Gogh, who himself suffered from depression and committed suicide, painted this picture in 1890 of a man that can symbolize the desperation and hopelessness felt in depression.
Clinical depression (also called major depressive disorder, or sometimes unipolar when compared with bipolar disorder, which is sometimes called manic depression) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individual's social functioning and/or activities of daily living. Although a low mood or state of dejection that does not affect functioning is often colloquially referred to as "depression", clinical depression is a clinical diagnosis and may be different from the everyday meaning of "being depressed."
Many people identify the feeling of being depressed as "feeling sad for no reason", or "having no motivation to do anything." One suffering from depression may feel tired, sad, irritable, lazy, unmotivated, and apathetic. Clinical depression is generally acknowledged to be more serious than normal depressed feelings. It often leads to constant negative thinking and sometimes substance abuse.
Depression is sometimes a comorbid condition with Asperger syndrome, and is treated with antidepressant medication.