Everyone experiences some unhappiness, often as a result of a life change, either in the form of a setback or a loss, or simply, as Freud said, "everyday misery." The painful feelings that accompany these events are usually appropriate and temporary, and can even present an opportunity for personal growth and improvement. However, when sadness persists and impairs daily life, it may indicate a depressive disorder. Severity, duration, and the presence of other symptoms are the factors that distinguish normal sadness from clinical depression.
Clinical depression is classified as a mood disorder. The primary subtypes are major depression, dysthymia (longstanding but milder depression), and atypical depression. Other depressive disorders include premenstrual dysphoric disorder (PDD or PMDD) and seasonal affective disorder (SAD).
The other major mood disorder is bipolar disorder, formerly called manic-depressive illness, which is characterized by periods of depression alternating with episodes of excessive energy and activity. Bipolar disorder is not discussed in this report. [For more information, see In-Depth Report #66: Bipolar disorder.]
Major depression is also called major depressive disorder. In major depression, at least five of the symptoms listed below must occur for a period of at least 2 weeks, and they must represent a change from previous behavior or mood. Depressed mood or loss of interest must be present. Symptoms include:
1. Depressed mood on most days for most of each day -- irritability may be prominent in children and adolescents
2. Total or very noticeable loss of pleasure most of the time
3. Significant increases or decreases in appetite, weight, or both
4. Sleep disorders, either insomnia or excessive sleepiness, nearly every day
5. Feelings of agitation or a sense of intense slowness
6. Loss of energy and a daily sense of tiredness
7. Sense of guilt or worthlessness nearly all the time
8. Inability to concentrate occurring nearly every day
9. Recurrent thoughts of death or suicide
In addition, other criteria must be met:
- The symptoms listed above do not follow or accompany manic episodes (such as in bipolar disorder or other disorders).
- They impair important normal functions (such as work or personal relationships).
- They are not caused by drugs, alcohol, or other substances.
- They are not caused by normal grief.
Review Date: 01/27/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.