July 1st 2007The diagnostic criteria for major depression are anhedonia, depressed mood, feelings of worthlessness or inappropriate guilt, inability to concentrate, fatigue, insomnia or hypersomnia, psychomotor agitation or retardation, significant weight loss or gain, and recurrent thoughts of death or suicide. Five or more of these symptoms must be present for at least 2 weeks, and one of them must be anhedonia or depressed mood. Conditions that can present with depression include dysthymia, bipolar disorder, cyclothymia, and adjustment disorder. Depression may also result from substance abuse or from the physiological conditions associated with a medical disorder, such as spinal or head injury, AIDS, or cancer.