Feelings of 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. But true clinical depression is a mood disorder in which feelings of sadness, loss, anger, or frustration interfere with everyday life for an extended period of time.

See also depression in the elderly and adolescent depression.

Depression is generally ranked in terms of severity -- mild, moderate, or severe. The degree of your depression, which your doctor can determine, influences how you are treated. Symptoms of depression include:

• Sleep disturbances -- usually insomnia (for example, consistently waking up very early in the morning) but may be excessive sleeping
• A dramatic change in appetite, often resulting in either weight gain or weight loss
• Fatigue and lack of energy
• Feelings of worthlessness, self-hate, and inappropriate guilt
• Extreme difficulty concentrating
• Agitation, restlessness, and irritability OR inactivity and withdrawal from usual activities
• Recurring thoughts of death or suicide
• Feelings of hopelessness and helplessness

Low self esteem is common with depression. So are sudden bursts of anger and lack of pleasure from activities that normally make you happy, including sex.

The main types of depression include:

• Major depression -- five or more symptoms listed above must be present for at least 2 weeks, but tends to continue for 20 weeks. (A mood disorder is classified as minor depression if less than five depressive symptoms are present for at least 2 weeks.)
• Dysthymia -- a chronic, generally milder form of depression but lasts longer -- usually as long as two years.
• Atypical depression -- depression accompanied by unusual symptoms, such as hallucinations (for example, hearing voices that are not really there) or delusions (irrational thoughts).

Other common forms of depression include:

• Postpartum depression -- many women feel somewhat down after having a baby, but true postpartum depression is rare.
• Premenstrual dysphoric disorder (PDD) -- depressive symptoms occur one week prior to menstruation and disappear after you menstruate.
• Seasonal affective disorder (SAD) -- occurs during the fall-winter season and disappears during the spring-summer season. Likely to be due to lack of sunlight.

Depression may also occur with mania (known as manic-depression or bipolar disorder). In this condition, moods cycle between mania and depression.

Depression is more common in women than men and is especially common during the teen years. Men seem to seek help for feelings of depression less often than women. Therefore, women may only have more documented cases of depression.

Depression often runs in families. This may be from heredity, learned behavior, or both. Even with a genetic predisposition, it is usually a stressful or unhappy life event that triggers the onset of a depressive episode.

Depression may be brought on by:

• Disappointment at home, work, or school (in teens, this may be breaking up with a boyfriend or girlfriend, failing a class, or parents divorcing)
• Death of a friend or relative
• Prolonged pain or having a major illness
• Medical conditions such as hypothyroidism (under-active thyroid), cancer, or hepatitis
• Drugs such as sedatives for sleep or anxiety and certain high blood pressure medications
• Alcohol or drug abuse
• Chronic stress
• Childhood events like abuse or neglect
• Social isolation (common in the elderly)
• Nutritional deficiencies (such as folate and omega-3 fatty acids)

• Sleeping problems

If you have depressive symptoms for two weeks or longer, you should contact your doctor, who can offer treatment options. Regardless of whether you have mild or major depression, the following self-care measures can help:

• Get adequate and regular sleep.
• Follow a healthy, nutritious diet.
• Exercise regularly.
• Avoid the use of alcohol, marijuana, and other recreational drugs.
• Stay involved in activities that normally make you happy, even if you don't feel like it.
• Spend time with family and friends.
• Try talking to clergy or spiritual advisers who may help give meaning to painful experiences.
• Consider prayer, meditation, tai chi, or biofeedback as ways to relax or draw on your inner strengths.

It may be helpful to add omega-3 fatty acids to your diet, which you can get from cold-water fish like tuna, salmon, or mackerel. Also, taking folate (vitamin B9) may be helpful. Appropriate amounts of folate (400 to 800 micrograms) are found in many multivitamins.

If your depression occurs in the fall or winter months, try light therapy using a special lamp that mimics the sun.

Many people try a popular over-the-counter herb called St. John's Wort. Some studies do suggest that this herbal remedy may be helpful for mild depression, but not moderate or severe. Be aware that St. John's Wort has a lot of potential drug interactions and should NOT be taken with prescription antidepressants, birth control pills, protease inhibitors for HIV, theophylline, warfarin, digoxin, reserpine, cyclosporine, or loperamide. Talk to your doctor if you are thinking about trying this herb for mild depression.

If you have moderate to severe depression, the most effective treatment plan will likely be a combination of counseling and medication.

Call your local emergency number (such as 911), a suicide hotline, or get safely to a nearby emergency room if you have thoughts of suicide, a suicidal plan, or thoughts of harming yourself or others.

Call your doctor right away if:

• You hear voices that are not there.
• You have frequent crying spells with little or no provocation.
• You have had feelings of depression that disrupts work, school, or family life for longer than two weeks.
• You have three or more depressive symptoms.
• You think that one of your current medications may be making you feel depressed. DO NOT change or stop any medications without consulting your doctor.
• You believe that you should cut back on drinking, a family member or friend has asked you to cut back, you feel guilty about the amount of alcohol you drink, or you drink alcohol first thing in the morning.

A complete history, a psychiatric interview and a physical examination will be performed to try to classify your depression as mild, moderate, or severe and to see if there is an underlying, treatable cause (such as alcohol abuse or an underactive thyroid). Hospitalization is usually recommended if suicide seems possible.

Expect some exploration of the issues and events associated with your feelings of depression. Your doctor will ask you about:

• Your depressive moods and other associated symptoms (sleep, appetite, concentration, energy).
• Possible stressors in your life, and support systems in place.
• Whether thoughts about ending your life have ever crossed your mind.
• Drug and alcohol use, and about the medications you are currently taking, if any.

Treatment will vary according to the cause and severity of your depressive symptoms, as well as your personal preference. The most effective therapy for moderate or severe depression is a combination of antidepressant medication and psychotherapy.

For mild depression, counseling and self-care measures without medication may be enough.

If you are taking medications for other purposes that could cause depression as a side effect, these may need to be changed. DO NOT change or stop any of your medications without consulting your doctor.

For people who are so severely depressed as to be unable to function, or who are suicidal and cannot be safely cared for in the community, psychiatric hospitalization may be necessary.

Healthy lifestyle habits can help prevent depression, or lessen the chances of it happening again. These habits include eating properly, sleeping adequately, exercising regularly, learning to relax, and not drinking alcohol or using drugs.

Counseling may help you through times of grief, stress, or low mood. Family therapy may be particularly important for teens who feel blue.

For elderly or others who feel socially isolated or lonely, try volunteering or getting involved in group activities.