Diagnosis of major depression is based on standard clinical criteria such as those published by the American Psychiatric Association. The criteria for the diagnosis of an episode include at least two weeks of depressed mood, loss of interest, or diminished sense of pleasure plus four of seven other features that are sufficient to cause clinically important psychological or physical distress or functional impairment. These features include a weight change of 5 percent or more in one month or a persistent change in appetite, insomnia or hypersomnia on most days, changes in psychomotor state, fatigue, feelings of guilt and worthlessness, diminished concentration and decisiveness, and suicidal ideation or a suicide attempt. First or “early” depressive episodes are often milder than are episodes of returning depression, and an earlier age at onset generally predicts a more severe course. It is thought that early diagnosis and treatment may mitigate adverse effects of depression on education, career, and relationships.