Depression is different from ordinary sadness. With true sadness, the person experiences a negative event, cries, and grieves over what happened. Afterward, the person feels a little bit better. Each time the person expresses sadness and grief, they are that much closer to a sense of healing.

Depression, on the other hand, occurs when the person falls into a pattern of negative thinking and inactivity. It is associated with feelings of hopelessness and helplessness. After an episode of depression the person does not feel any better, and is not any closer to healing.

Depression occurs in different forms. The three most common kinds are:

1. Major Depression, where there is a depressed mood or a loss of interest in activities that were previously enjoyed. The symptoms occur almost every day, for most of the day, and persist for at several weeks or months (in contrast to a passing blue mood). In addition to a low mood and loss of interest, several other symptoms are present, such as disturbances in sleep and energy level; changes in appetite; difficulties with making everyday decisions, concentrating, and remembering; feelings of worthlessness, hopelessness or guilt; self-critical thoughts, and thoughts of suicide. Major Depression often results in impairment in work, school, or social functioning.

2. Dysthymia is more chronic (two years or more) but less severe than Major Depression. The main features are a depressed mood and low self-esteem. A low energy level, and sleep and appetite disturbances, are frequently seen as well.

It is not unusual for people with Dysthymia to report to report that they have felt depressed for virtually their entire life. While Dysthymia does not result in the same degree of impairment in functioning as is usually seen in Major Depression, it frequently leads to problems in specific life areas, such as meeting certain work or family responsibilities, or initiating or maintaining interpersonal relationships.

3. Bipolar Disorder (also called manic-depression) is marked by severe mood changes: severe highs (mania) and lows (depression). Sometimes the mood swings are dramatic and rapid, but more frequently they are gradual. Mania occurs when the person feels either unusually energetic and confident or unusually irritable and belligerent. Also typical of a manic episode are a decreased need for sleep, racing thoughts, talkativeness, increased activity, and impulsive behavior such as spending sprees or sexual indiscretions. The depressive episode is the same as that observed in a Major Depression described above.