Definition of Depression:

Depression may be described as feeling sad, blue, unhappy, miserable, or down in the dumps. Most of us feel this way at one time or another for short periods.

Clinical depression is a mood disorder in which feelings of sadness, loss, anger, or frustration interfere with everyday life for a longer period of time.

For more information on the symptoms and treatment of depression, see:

• Adolescent depression
• Bipolar disorder
• Depression in the elderly
• Dysthymia
• Major depression

Considerations:

Symptoms of depression include:

• Low or irritable mood most of the time
• A loss of pleasure in usual activities
• Trouble sleeping or sleeping too much
• A big change in appetite, often with weight gain or loss
• Tiredness and lack of energy
• Feelings of worthlessness, self-hate, and guilt
• Difficulty concentrating
• Slow or fast movements
• Lack of activity and avoiding usual activities
• Feeling hopeless or helpless
• Repeated thoughts of death or suicide

Low self-esteem is common with depression. It is also common to have sudden bursts of anger and a lack of pleasure from activities that normally make you happy, including sex.

Depressed children may not have the same symptoms as adult depression. Watch for changes in school work, sleep, and behavior. If you wonder whether your child might be depressed, it's worth talking to a health care provider.

The main types of depression include:

• Major depression -- to be diagnosed with major depression, you must have five or more of the symptoms listed above for at least 2 weeks. Major depression tends to continue for at least 6 months if not treated. (You are said to have minor depression if you have less than five depression symptoms for at least 2 weeks. Minor depression is similar to major depression except it only has two to four symptoms.)
• Atypical depression -- occurs in about a third of patients with depression. Symptoms include overeating and oversleeping. You may feel like you are weighed down and get very upset by rejection.
• Dysthymia -- a milder form of depression that can last for years, if not treated.

Other common forms of depression include:

• Postpartum depression -- many women feel somewhat down after having a baby, but true postpartum depression is more severe and includes the symptoms of major depression.
• Premenstrual dysphoric disorder (PMDD) -- symptoms of depression occur 1 week before your menstrual period and disappear after you menstruate.
• Seasonal affective disorder (SAD) -- occurs most often during the fall-winter season and disappears during the spring-summer season. It is most likely due to a lack of sunlight.

Depression may also alternate with mania (known as manic depression or bipolar disorder).

Depression may be more common in women than men. This may be because women tend to seek help for it more. Depression is also more common during the teenage years.

Common Causes:

Depression often runs in families. This may be due to your genes (inherited), behaviors you learn at home, or both. Even if your genes make you more likely to develop depression, a stressful or unhappy life event usually triggers the depression.

Many factors can cause depression, including:

• Alcohol or drug abuse
• Medical conditions and treatments, such as:
  • Certain types of cancer
  • Long-term pain
  • Sleeping problems
  • Steroid medications
  • Underactive thyroid (hypothyroidism)
• Stressful life events, such as:
  • Abuse or neglect
  • Breaking up with a boyfriend or girlfriend
  • Certain types of cancer
  • Death of a relative or friend
  • Divorce, including a parent's divorce
  • Failing a class
  • Illness in the family
  • Job loss
  • Long-term pain
  • Social isolation (common cause of depression in the elderly)