Everybody gets the blues now and then - but for millions of Americans, depressive illnesses are more serious than that. They are persistent, recurring conditions that can interfere with a person's ability to sleep, eat, and hold a job and can last for weeks or months at a time. Major depression is a very common and serious medical illness. Often, depression run in families.
Depressed people have unusual brain chemistry patterns.
Serious depression may however occur even in the absence of any significant life stress. Depression is very responsive to treatment. Most people will feel markedly improved within 6-8 weeks of treatment. Another form of the disorder is manic-depression in which a person swings between excessive euphoria and depression. The exact cause of depression is not known.