Major depression is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Nearly five million of the 31 million Americans who are 65 years or older are clinically depressed, and one million have major depression. Approximately 3% of healthy elderly persons living in the community have major depression. Recurrence may be as high as 40%. Suicide rates are nearly twice as high in depressed patients as in the general population. Major depression is more common in medically ill patients who are older than 70 years and hospitalized or institutionalized. Severe or chronic diseases associated with high rates of depression include stroke (30–60%), coronary heart disease (8–44%), cancer (1–40%), Parkinson's disease (40%), Alzheimer's disease (20–40%), and dementia (17–31%). Minor depression is a clinically significant depressive disorder that does not fulfill the duration criterion or the number of symptoms necessary for the diagnosis of major depression. Minor depression, which is more common than major depression in elderly patients, may follow a major depressive episode. It also can be a reaction to routine stressors in older populations. 15–50% of patients with minor depression develop major depression within two years.
Late life depression
Depression 
Retarded depression
Double depression
Treatment-resistant depression
Outline of bipolar disorder
Depression in childhood and adolescence
Personality pathology