Major depression is when five or more symptoms of depression are present for at least 2 weeks. These symptoms include feeling sad, hopeless, worthless, or pessimistic. In addition, people with major depression often have behavior changes, such as new eating and sleeping patterns. Major depression increases a person's risk of suicide.

The exact cause of depression is not known. Many researchers believe it is caused by chemical imbalances in the brain, which may be hereditary or caused by events in a person's life.

Some types of depression seem to run in families, but depression can also occur in people who have no family history of the illness. Stressful life changes or events can trigger depression in some people. Usually, a combination of factors is involved.

Each year, more than 18 million Americans -- men and women of all ages, races, and economic levels -- have depression. It occurs more often in women.

Women are especially vulnerable to depression after giving birth. This is a result of the hormonal and physical changes. While new mothers commonly experience temporary "blues," depression that lasts longer than 2-3 weeks is not normal and requires treatment.

Major depression can occur in children and teenagers, and they can also benefit from treatment.

See also: Adolescent depression

• Trouble sleeping or excessive sleeping
• A dramatic change in appetite, often with weight gain or loss
• Fatigue and lack of energy
• Feelings of worthlessness, self-hate, and inappropriate guilt
• Extreme difficulty concentrating
• Agitation, restlessness, and irritability
• Inactivity and withdrawal from usual activities, a loss of interest or pleasure in activities that were once enjoyed (such sex)
• Feelings of hopelessness and helplessness
• Thoughts of death or suicide

Depression can appear as anger and discouragement rather than feelings of hopelessness and helplessness. If depression is very severe, it may be accompanied by psychotic symptoms, such as hallucinations and delusions. These are usually consistent with the depressed mood, and may focus on themes of guilt, personal inadequacy, or disease.

Major depression is diagnosed if the person reports having five or more depressive symptoms for at least 2 weeks. Beck's Depression Scale Inventory or other screening tests for depression can be helpful in diagnosing depression.

Medical causes that can cause symptoms of depression should also be ruled out before making the diagnosis of depression.

Depression can be treated in a variety of ways, particularly with medications and counseling. Most people benefit from a combination of the two. Some studies have shown that antidepressant drug therapy combined with psychotherapy appears to have better results than either therapy alone.

Medications include tricyclic antidepressants, monoamine oxidase inhibitors, selective serotonin re-uptake inhibitors (SSRIs), and some newer antidepressant drugs. While antidepressant medications can be very effective, some may not be appropriate for everyone. For example, in September, 2004 the FDA began considering a warning that some antidepressants may increase the risk of suicidal tendencies in children. In 2007, the FDA proposed that all antidepressant medicines should warn of the risk of suicidal behavior in young adults ages 18 - 24 years.

Lithium and thyroid supplements may be needed to enhance the effectiveness of antidepressants. For persons with psychotic symptoms, such as delusions or hallucinations, antipsychotic medications may be needed.

Electroconvulsive therapy (ECT) is a treatment that causes a seizure by means of an electrical current. ECT may improve the mood of severely depressed or suicidal people who don't respond to other treatments.

Research is now being conducted on transcranial magnetic stimulation (TMS), which alters brain functioning in a way similar to ECT, but with fewer side effects. Use of light therapy for depressive symptoms in the winter months and interventions to restore a normal sleep cycle may be effective in relieving depression.

As treatment takes effect, negative thinking diminishes. It takes time to feel better, but there are usually day-to-day improvements. It is important to maintain a healthy lifestyle. Eat well-balanced meals, avoid alcohol and drugs (which make depression worse and may interfere with medications), get regular exercise and sleep, and seek supportive interpersonal relationships.

Many consumers try herbal products for depression. St. John's wort has a long history of use in Germany and has gained popularity as an herbal antidepressant in the United States. Most of the German studies indicated that St. John's wort was comparable to some antidepressants. However, a large study conducted by the National Center for Complementary and Alternative Medicine found that St. John's wort was NOT effective for treating major depression.

Because herbal products can have side effects, always tell your doctor if you are using them.

For more information and resources, see depression support group.

The outcome is usually good with treatment. Although most depressive episodes can be effectively treated with either medication, psychotherapy, or both, depression is a recurring problem for many people. For people who have experienced repeated episodes of depression, maintenance treatment may be needed to prevent future recurrences.

• Suicide (up to 15% of people with major depressive disorder die by suicide)
• Increased risk of alcohol- and drug-related problems
• Increased risk of tobacco dependence
• Increased risk of problems with physical health and premature death due to medical illness

Call 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 disrupt work, school, or family life for longer than 2 weeks.
• 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.

Some episodes of depression can be avoided by:

• Learning how to relax and manage stress
• Avoiding alcohol, drugs, and caffeine
• Exercising regularly
• Maintaining good sleep habits

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.

Medications and psychiatric counseling may prevent recurrences. Some episodes of depression are not preventable.