Depression is a common but serious illness which interferes with daily life, the ability to work, sleep, study, eat, and enjoy life.

Depression is caused by a combination of genetic, biological, environmental, and psychological factors. Some genetics research indicates that risk for depression results from the influence of several genes acting together with environmental or other factors. Some types of depression tend to run in families. However, depression can occur in people without family histories of depression too. People with depressive illnesses do not all experience the same symptoms. The severity, frequency, and duration of symptoms vary depending on the individual and his or her particular illness.