But medical information is always changing, and some information given here may be out of date. For regularly updated information on a variety of health topics, please visit familydoctor.org , the AAFP patient education Web site. Depression is a medical illness like diabetes or high blood pressure. People don't choose to be depressed.
Depression is an illness.
It affects about 17 percent of people at some time in their lives. It's twice as common in women as in men. The exact cause of depression is not known. Doctors think it may be caused by a chemical imbalance in the brain. The imbalance could be caused by your genes or by events in your life.