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Depression is a disorder that affects your thoughts, moods, feelings, behavior and even your physical health. People used to think it was "all in your head" and that if you really tried, you could "snap out of it" or just "get over it." But doctors now know that depression is not a weakness, and it's not something you can treat on your own. Depression is a medical disorder with a biological and chemical basis.

Sometimes a stressful life event triggers depression. Other times depression seems to occur spontaneously with no identifiable specific cause. Depression is much more than grieving or a bout of the blues.

Depression may occur only once in a person's life. Often, however, it occurs as repeated episodes over a lifetime, with periods free of depression in between. Or it may be a chronic condition, requiring ongoing treatment over a lifetime.

People of all ages and races suffer from depression. Medications are available that are generally safe and effective, even for the most severe depression. With proper treatment, most people with serious depression improve, often within weeks, and can return to normal daily activities.

Two hallmarks of depression — symptoms key to establishing a diagnosis — are:

• Loss of interest in normal daily activities. You lose interest in or pleasure from activities that you used to enjoy.
• Depressed mood. You feel sad, helpless or hopeless, and may have crying spells.

In addition, for a doctor or other health professional to diagnose depression, most of the following signs and symptoms also must be present for at least two weeks.

• Sleep disturbances. Sleeping too much or having problems sleeping can be a sign you're depressed. Waking in the middle of the night or early in the morning and not being able to get back to sleep are typical.
• Impaired thinking or concentration. You may have trouble concentrating or making decisions and have problems with memory.
• Changes in weight. An increased or reduced appetite and unexplained weight gain or loss may indicate depression.
• Agitation. You may seem restless, agitated, irritable and easily annoyed.
• Fatigue or slowing of body movements. You feel weariness and lack of energy nearly every day. You may feel as tired in the morning as you did when you went to bed the night before. You may feel like you're doing everything in slow motion, or you may speak in a slow, monotonous tone.
• Low self-esteem. You feel worthless and have excessive guilt.
• Less interest in sex. If you were sexually active before developing depression, you may notice a dramatic decrease in your level of interest in having sexual relations.
• Thoughts of death. You have a persistent negative view of yourself, your situation and the future. You may have thoughts of death, dying or suicide.

Depression can also cause a wide variety of physical complaints, such as gastrointestinal problems (indigestion, constipation or diarrhea), headache and backache. Many people with depression also have symptoms of anxiety.

Children, teens and older adults may react differently to depression. In these groups, symptoms may take different forms or may be masked by other conditions. Kids may pretend to be sick, worry that a parent is going to die, perform poorly in school, refuse to go to school, or exhibit behavioral problems. Older people may be more willing to discuss the physical manifestations of depression, instead of their emotional difficulties.

Types of depression
The main types of depression include:

• Major depression. This type of mood disturbance lasts more than two weeks. Symptoms may include overwhelming feelings of sadness and grief, loss of interest or pleasure in activities you usually enjoy, and feelings of worthlessness or guilt. This type of depression may result in poor sleep, a change in appetite, severe fatigue and difficulty concentrating. Severe depression may increase the risk of suicide.
• Dysthymia. Dysthymia (dis-THI-me-uh) is a less severe but more chronic form of depression. Signs and symptoms usually aren't disabling, and periods of dysthymia can alternate with short periods of feeling normal. Having dysthymia places you at an increased risk of major depression.
• Adjustment disorders. If a loved one dies, you lose your job or you receive a diagnosis of cancer, it's perfectly normal to feel tense, sad, overwhelmed or angry. Eventually, most people come to terms with the lasting consequences of life stresses, but some don't. This is what's known as an adjustment disorder — when your response to a stressful event or situation causes signs and symptoms of depression. Some people develop an adjustment disorder in response to a single event. In others, it stems from a combination of stressors. Adjustment disorders can be acute (lasting less than six months) or chronic (lasting longer). Doctors classify adjustment disorders based on the primary signs and symptoms of depression or anxiety.
• Bipolar disorder. Having recurrent episodes of depression and elation (mania) is characteristic of bipolar disorder. Because this condition involves emotions at both extremes (poles), it's called bipolar disorder or manic-depressive disorder. Mania affects your judgment, causing you to make unwise decisions. Some people have bursts of increased creativity and productivity during the manic phase. The number of episodes at either extreme may not be equal. Some people may have several episodes of depression before having another manic phase, or vice versa.
• Seasonal affective disorder. Seasonal affective disorder (SAD) is a pattern of depression related to changes in seasons and a lack of exposure to sunlight. It may cause headaches, irritability and a low energy level.

There's no single known cause for depression. The illness often runs in families. Experts believe a genetic vulnerability combined with environmental factors, such as stress or physical illness, may trigger an imbalance in brain chemicals called neurotransmitters, resulting in depression. Imbalances in three neurotransmitters — serotonin, norepinephrine and dopamine — seem to be linked to depression.

Scientists don't fully understand how imbalances in neurotransmitters cause signs and symptoms of depression. It's not certain whether changes in neurotransmitters are a cause or a result of depression.

Factors that contribute to depression include:

• Heredity. Researchers have identified several genes that may be involved in bipolar disorder, and they're looking for genes linked to other types of depression. But not everyone with a family history of depression develops the disorder, and conversely, people with no family history of the disorder can become depressed.
• Stress. Stressful life events, particularly a loss or threatened loss of a loved one or a job, can trigger depression.
• Medications. Long-term use of certain medications, such as some drugs used to control high blood pressure, sleeping pills or, occasionally, birth control pills, may cause symptoms of depression in some people.
• Illnesses. Having a chronic illness, such as heart disease, stroke, diabetes, cancer or Alzheimer's disease, puts you at higher risk of developing depression. Having an underactive thyroid (hypothyroidism), even mildly, also can cause depression.
• Personality. Certain personality traits, such as having low self-esteem and being overly dependent, self-critical, pessimistic and easily overwhelmed by stress, can make you more vulnerable to depression.
• Postpartum depression. It's common for mothers to feel a mild form of distress that usually occurs a few days to weeks after giving birth. During this time you may have feelings of sadness, anger, anxiety, irritability and incompetence. A more severe form of the baby blues, called postpartum depression, also can affect new mothers.
• Hormones. Women experience depression about twice as much as men, which leads researchers to believe hormonal factors may play a role in the development of depression.
• Alcohol, nicotine and drug abuse. Experts once thought that people with depression used alcohol, nicotine and mood-altering drugs as a way to ease depression. But using these substances may actually contribute to depression and anxiety disorders.

Depression affects all ages and all races. Twice as many women experience depression as men. While men are less likely to become depressed than women are, depression does affect men as well. Gender differences in depression may be due in part to biological causes, such as hormones and different levels of neurotransmitters.

Other factors that may put you at an increased risk of depression include a family history of the disorder, pregnancy or stressful life events, such as the loss of a loved one or a job.

If you show little interest in once-enjoyable activities, if you feel sad, helpless, tired or worthless, and if your eating and sleeping habits have changed greatly, see your doctor to determine if you have depression. If you know someone who exhibits the characteristics of depression, encourage him or her to seek professional help.

To diagnose depression, your doctor may perform a physical examination, including tests to rule out conditions that can cause symptoms that mimic depression.

If your doctor sees signs of severe depression or suspects the possibility of suicide, he or she may refer you to a medical doctor who specializes in mental illness (psychiatrist) or even recommend immediate hospitalization.

Your doctor or psychiatrist diagnoses depression based on the hallmark signs and symptoms of the disease, plus the presence of other signs and symptoms that typically accompany depression.

Depression is a serious illness that can take a terrible toll on individuals and families. Untreated, depression can lead to a downward spiral of disability, dependency and suicide. Women attempt suicide more often than men do, but men are much more likely to succeed in killing themselves. The rate of suicide is four times greater for men. Men over 70 are the most likely to commit suicide.

Certain warning signs may indicate serious depression and the possibility of suicide. Take any threat of suicide seriously, even if the person is already being treated for depression. If you see any of the following danger signs, call a doctor, mental health clinic or suicide hot line immediately:

• Pacing, agitated behavior, frequent mood changes and sleeplessness for several nights
• Actions or threats of assault, physical harm or violence
• Threats or talk of death or suicide, such as "I don't care anymore," or "You won't need to worry about me much longer"
• Withdrawal from activities and relationships
• Putting affairs in order, such as saying goodbye to friends, giving away prized possessions or writing a will
• A sudden brightening of mood after a period of being depressed
• Unusually risky behavior, such as buying or handling a gun or driving recklessly

The development of newer antidepressant medications and mood-stabilizing drugs has improved the treatment of depression. Medications can relieve symptoms of depression and have become the first line of treatment for most types of the disorder.

Treatment may also include psychotherapy, which may help you cope with ongoing problems that may trigger or contribute to depression. A combination of medications and a brief course of psychotherapy usually is effective if you have mild to moderate depression. If you're severely depressed, initial treatment usually is with medications or electroconvulsive therapy. Once you improve, psychotherapy can be more effective.

Doctors usually treat depression in two stages. Acute treatment with medications helps relieve symptoms until you feel well. Once your symptoms ease, maintenance treatment typically continues for four to nine months to prevent a relapse. It's important to keep taking your medication even though you feel fine and are back to your usual activities. Episodes of depression recur in the majority of people who have one episode, but continuing treatment greatly reduces your risk of a rapid relapse. If you've had two or more previous episodes of depression, your doctor may suggest long-term treatment with antidepressants.

Medications

• Selective serotonin reuptake inhibitors (SSRIs). Doctors often consider selective serotonin reuptake inhibitors, such as fluoxetine (Prozac, Sarafem), paroxetine (Paxil), sertraline (Zoloft), citalopram (Celexa) and escitalopram (Lexapro), as the first-line treatment for depression because they have fewer serious side effects. They seem to work by increasing the availability of the neurotransmitter serotonin in your brain. Drugs similar to SSRIs include serotonin and norepinephrine reuptake inhibitors (SNRIs), such as trazodone (Desyrel) and venlafaxine (Effexor), and dopamine reuptake inhibitors, such as bupropion (Wellbutrin).
• Tricyclic and tetracyclic antidepressants. These medications also affect neurotransmitters, but by a different mechanism than SSRIs. They may be used for any type of depression, be it mild or severe. Among tricyclic antidepressants are amitriptyline, desipramine (Norpramin), nortriptyline (Aventyl, Pamelor), protriptyline (Vivactil), trimipramine (Surmontil) and a combination of perphenazine and amitriptyline. Tetracyclics include maprotiline and mirtazapine (Remeron).
• Monoamine oxidase inhibitors (MAOIs). These drugs, which include phenelzine (Nardil) and tranylcypromine (Parnate), prevent the breakdown of neurotransmitters. The drugs have potentially serious side effects if combined with certain other medications or food products. Doctors rarely use them unless other options have failed. Your doctor may prescribe them if you have chronic depression and eat or sleep excessively.
• Stimulants. Your doctor may initially prescribe a stimulant such as methylphenidate (Ritalin, Concerta), dextroamphetamine (Dexedrine, Dextrostat) or modafinil (Provigil) if you can't take antidepressants because they're contraindicated due to another medical condition. These medications are also sometimes given in conjunction with antidepressants.
• Lithium and mood-stabilizing medications. Doctors prescribe lithium (Eskalith, Lithobid), valproic acid (Depakene), divalproex (Depakote) and carbamazepine (Tegretol, Carbatrol) to treat bipolar depression. Medications called atypical antipsychotics such as olanzapine (Zyprexa), risperidone (Risperdal) and quetiapine (Seroquel) were initially developed for treatment of psychotic disorders. Doctors sometimes also use them to treat bipolar disorder.

According to the American Diabetes Association (ADA), certain antipsychotic drugs may increase the risk of diabetes, obesity and high blood pressure. That's why the ADA recommends that doctors screen and monitor anyone taking Risperdal, Seroquel and Zyprexa.

Not everyone responds the same way
Most antidepressants have a similar level of effectiveness. But a medication that works for someone else might not work for you. Doctors choose antidepressants based on your family history and the match between your symptoms and the medication's side effects. For example, if you have insomnia, a sedating antidepressant may help you. But if you're lethargic, then a more energizing antidepressant may be more helpful.

It can take up to eight to 12 weeks before you feel the full effects of an antidepressant, though you may feel some changes earlier. If your response to medication hasn't resulted in satisfactory progress after that time, your doctor may suggest either adding another antidepressant or replacing the first medication with another drug from a different chemical family.

Side effects of medications
As with any medication, side effects are possible. You may notice side effects before you can feel the drug begin to ease your depression. Most of the side effects from antidepressant are temporary and will disappear as your body gets used to the medication. Let your doctor know about any side effects that interfere with daily functioning, or if they're especially bothersome.

• SSRIs. Side effects that may occur with SSRIs and other new antidepressants include headache, nausea, insomnia, agitation or a jittery feeling, and sexual difficulties.
• Tricyclic antidepressants. Older medications, such as tricyclics, may cause dry mouth, constipation, sexual difficulties, blurred vision, dizziness, bladder problems and daytime drowsiness.
• MAOIs. These drugs can cause a significant increase in blood pressure if you eat foods high in tyramine, such as wine, cheese or pickles, or if you take certain drugs, such as decongestants, while taking an MAOI. Ask your doctor or pharmacist for a list of foods and drugs to avoid.

Alcohol can interfere with the way your body absorbs antidepressants. Talk with your doctor before drinking alcohol while you're taking an antidepressant.

Concerns with children and teens
In children and teenagers, there's some concern that the use of antidepressants to treat major depression may lead to an increased risk of suicide — from about 2 percent for children not taking these medications to 4 percent for children taking an antidepressant for major depression. Physicians, parents and children need to weigh the benefits of these medications against the potential risks. Because of the increased risk, the Food and Drug Administration (FDA) directed manufacturers of antidepressants to include a warning on the medication that explains the risk and recommends that children be closely observed by their families, caregivers and physicians while on these medications.

Other treatments
In addition to medications, depression treatment may include:

• Psychotherapy. There are several types of psychotherapy. Each type involves a short-term, goal-oriented approach aimed at helping you deal with a specific issue. Prolonged psychotherapy is seldom necessary to treat depression. If an underlying factor contributing to your depression is an inability to get along with others or difficulty finding your place in life, then prolonged psychotherapy could help you.

  The success of therapy depends on finding a doctor, psychiatrist or psychologist you're comfortable with. Both medications and psychotherapy can take weeks to have an effect. Specialized and supervised group therapy, such as bereavement groups, stress management classes, marital counseling and family therapy, also may help.

• Electroconvulsive therapy. Despite the images that many people conjure up, electroconvulsive therapy is generally safe and effective. Experts aren't sure how this therapy relieves the signs and symptoms of depression. The procedure may affect levels of neurotransmitters in your brain. The most common side effect is confusion that lasts a few minutes to several hours. Some people experience some transient memory loss. This therapy is usually used for people who don't respond to medications and for those at high risk of suicide. It may be the only treatment available for severely depressed older adults who can't take medications because of heart disease.
• Light therapy. This therapy may help if you have seasonal affective disorder. This disorder involves periods of depression that recur at the same time each year, usually when days are shorter in the fall and winter. Scientists believe fewer hours of sunlight may increase levels of melatonin, a brain hormone thought to induce sleep and depress mood. Treatment in the morning with a specialized type of bright light, which suppresses production of melatonin, may help if you have this disorder.

Once treatment for depression begins, you still have to manage on a day-to-day basis. Here are some guidelines:

• See your doctor regularly. Your doctor can monitor your progress, provide support and encouragement, and adjust your medication if necessary.
• Take your medications. Finding the best medication for you may take several tries. It may take several weeks for you to start seeing results. Once you feel better, continue to take your medication as prescribed.
• Don't become isolated. Try to participate in normal activities.
• Take care of yourself. Eat a healthy diet and get the right amount of sleep and exercise. Exercise can help treat some forms of depression, ease stress and help you relax.
• Avoid alcohol and recreational drugs. Abuse of alcohol and drugs will slow or prevent your recovery.

Self-help organizations have become potent allies for people who are coping with mental illness or who care about someone with such an illness. For depression or other mental illnesses, self-help groups include:

• National Mental Health Association (NMHA): (800) 969-6642; or, in a crisis: (800) SUICIDE (784-2433)
• National Alliance for the Mentally Ill (NAMI): (800) 950-6264
• Depression and Bipolar Support Alliance: (800) 826-3632

Herbal and dietary supplements sold in stores have become increasingly popular. People take them to help prevent or treat a number of health conditions. Some of these alternative therapies are being studied to determine their effectiveness in helping depression. With additional studies, researchers may know more about these products, how effective they are and if they can cause other health problems or interfere with medications.

In the meantime, talk with your doctor before taking any herbal or dietary supplement. A problem with herbal and dietary products is that they aren't regulated. The FDA doesn't test them for safety, purity or effectiveness. That means you can't always be sure of what you're getting or if it's safe. Also, if you're already taking medications, herbal or dietary supplements may interfere with the way they work, or could cause dangerous interactions.

Some popular supplements marketed or taken for treatment of depression include:

• St. John's wort. St. John's wort is an herbal preparation from the Hypericum perforatum plant. It has long been used in folk medicine, and today it's widely prescribed in Europe to treat anxiety and depression. In the United States, it's sold in health food stores and pharmacies in the form of tablets or tea.

  European studies suggest that St. John's wort may work as well as antidepressants in mild depression and with fewer side effects. However, some studies have found that St. John's wort isn't effective in treating major depression. Adverse reactions include dry mouth, dizziness, digestive problems, fatigue, headache and sexual problems. In most cases, signs and symptoms are mild. Of concern is that St. John's wort can interfere with the effectiveness of prescription medications, including antidepressants, drugs to treat human immunodeficiency virus (HIV) infections and AIDS, and drugs to prevent organ rejection in people who've had transplants.

• SAM-e. Pronounced "sammy," short for S-adenosyl-methionine, this chemical substance is available in Europe as a prescription drug to treat depression. In the United States it's sold as an over-the-counter dietary supplement.

  SAM-e is a chemical substance found in all human cells and plays a role in many body functions. It's thought to increase levels of serotonin and dopamine. Some studies have found SAM-e to be more effective than a placebo, but no more effective than treatment with antidepressant medications. The pills are expensive, especially considering their effectiveness is unproved. SAM-e can cause nausea and constipation.

• 5-HTP. One of the raw materials that your body needs to make serotonin is a chemical called 5-HTP, which is short for 5-hydroxytryptophan. In theory, if you boost your body's level of 5-HTP, you should also elevate your levels of serotonin. But there's not enough evidence to determine if 5-HTP is effective and safe. Larger studies than have been conducted to date are needed.

• Omega-3 fatty acids. Omega-3 fatty acids are found in fish oil and certain plants. They're being studied as a possible mood stabilizer for people with bipolar depression and other psychiatric disorders.

  Fish oil capsules containing omega-3 fatty acids are sold in stores. The capsules are high in fat and calories and may produce gastrointestinal problems. Another way to get more omega-3 fatty acids is simply to eat more fish, tofu, soybeans, walnuts, or canola or flaxseed oil.