Major depression is when a person has five or more symptoms of depression 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.

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.

Men and women of all ages, races, and economic levels can have depression. It occurs more often in women.

Women are especially vulnerable to depression after giving birth. This is a result of hormonal and physical changes. Although 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

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

Depression can appear as anger and discouragement, rather than as feelings of hopelessness and helplessness. If depression is very severe, there may also be psychotic symptoms, such as hallucinations and delusions. These symptoms may focus on themes of guilt, inadequacy, or disease.

Major depression is diagnosed if a 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 making the diagnosis.

Before diagnosing depression, the health care provider should rule out medical conditions that can cause symptoms 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 treatments. Some studies have shown that antidepressant drug therapy combined with psychotherapy has better results than either therapy alone.

Medications include tricyclic antidepressants, monoamine oxidase inhibitors, selective serotonin re-uptake inhibitors (SSRIs), and some newer antidepressant drugs. Although antidepressant medications can be very effective, some may not be appropriate for everyone. For example, 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. People with psychotic symptoms, such as delusions or hallucinations, may need antipsychotic medications. The antipsychotic medication quetiapine has also been approved for treating episodes of depression in people with bipolar disorder.

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 function 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 for 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:

• Avoid alcohol and drugs (which make depression worse and may interfere with medications)
• Eat well-balanced meals
• Get regular exercise and sleep
• Seek supportive 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.

You may be able to avoid some episodes of depression by:

• Avoiding alcohol, drugs, and caffeine
• Exercising regularly
• Learning how to relax and manage stress
• 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.

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

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

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US Preventive Services Task Force. Guide to clinical preventive services: screening for depression, recommendations and rationale. 2002;136. Accessed October 17, 2008.

Conway MW, Miller MN. Mood disorders. In: Rakel P, Bope ET, eds. Conn's Current Therapy 2008. 60th ed. Philadelphia, Pa:Saunders Elsevier;2008:chap 281.

American Psychiatric Association. Practice guidelines for the treatment of patients with major depressive disorder. 2nd ed. September 2007. Accessed October 27, 2008.

Schiffer RB. Psychiatric disorders in medical practice. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa:Saunders Elsevier;2007:chap 420.