Depression is a biological condition that says no more about a person's character than having cancer or multiple sclerosis does. And it is surprisingly common. Studies indicate that between one in 10 and one in five Americans will go through an episode of clinical depression over the course of a lifetime. In any given year, as many as 17.5 Americans are clinically depressed.

The good news is that while clinical depression is common, it's also highly treatable. Today, 80% to 90% of people with a major depressive disorder will see their symptoms improve after treatment with antidepressant medications, psychotherapy, or electro convulsive therapy (ECT).

WHAT IS DEPRESSION ?

A lot of people don't recognize what depression is, or they don't acknowledge it as a medical illness, " says James W. Jefferson, M.D., distinguished senior scientist at the Dean Foundation for Health, Research and Education, and clinical professor of psychiatry at the University of Wisconsin Medical School. He says most surveys show that only about half of Americans consider clinical depression to be a biological disorder. "The other 50 percent think it's a sign of being weak and wimpy, and if you didn't let yourself go you could overcome it. That stands in the way of people getting help."

For most people, clinical depression is nothing like normal sadness. "We should have a different name for the syndrome that drains the zest for living and replaces it with anguish, guilt, pessimism, irritability, and the inability to experience pleasure," writes Jerrold F. Rosenbaum, M.D., a psychiatrist at Massachusetts General Hospital.

If a spouse dies, if a child marries and leaves home, if a person retires from a meaningful job, you expect to see a certain amount of grief and sadness. This is not depression -- it is a normal reaction to disturbing events that is usually temporary. Eventually, the sadness lifts.

Clinical depression, in contrast, may persist for months or even years, may deepen over time, and may be more disabling than most chronic illnesses. It has been described by some of its most famous sufferers (including Abraham Lincoln, Winston Churchill, and William Styron) as a "black dog" or a "howling tempest in the brain." As Dianne Hales and Robert E. Hales, M.D., write in their book Caring for the Mind: The Comprehensive Guide to Mental Health, for many sufferers, depression feels "like falling into a bottomless pit. Although sufferers want to escape, they cannot muster the strength to move."

Depressed people, they write, "feel themselves sliding into deeper, more terrifying depths, but they cannot help themselves or even hope that someone else might help them. They see no way out, and they may spend hours or days brooding about their past failures or future trials."

DOING WELL, FEELING BAD

Interestingly, major depression may arise just when life seems, objectively, to be going well. Many depressed people seem to have it all: good jobs, stable marriages, healthy children. But they get no joy out of the very things that make their lives look so full.

"My life had a big schism in it," recalls Nancy Welch. "On the one hand, I had significant success in both undergraduate and graduate school. I did really well academically, and landed fairly stellar employment (as an administrator at the Smithsonian Institution) by the age of 23. Professionally, I performed very well in my new career."

On the other hand, Welch had no normal life outside work. When she finally went home each night, she says, "I buried myself in sadness and in pain and in depression."

For some, depression can be a chronic, progressive condition that appears, disappears, and reappears over the course of a lifetime. The earlier it starts, the more likely it is to be followed by another bout at some time in the future. This is especially true if the depressed person just waits out the gloom, rather than seeking professional help at the first sign of trouble, says psychiatrist James Jefferson.

"After the first episode of major depression, the likelihood of having a second episode is at least 50 percent," says Jefferson. "That goes up with subsequent episodes, so once you have three or four, the likelihood of having another is 90-plus percent."

There is no blood test for depression, no pattern to spot on a brain scan. Instead, the diagnosis is based on the presence of symptoms including changes in eating and sleep patterns, loss of sexual desire, and lack of energy and concentration.

THE ROOTS OF DEPRESSION

Clinical depression is now recognized by many as a biological disorder, much like heart attack or diabetes. Scientists theorize that people with depression may have either too much or too little of certain brain chemicals, called neurotransmitters. These neurotransmitters allow brain cells to talk to one another. Scientists do not yet fully understand how neurotransmitters affect mood. But they do know some of the chemicals play an important role in the region of the brain that controls emotions.

Genetics also play a major role in determining who gets depressed and who doesn't. Someone whose mother or father suffered from depression runs a much higher than normal risk of becoming depressed. If both patents were depressed, the risk becomes significantly higher: each child runs a 50-50 chance of encountering depression.

Environment is important, too. Just because someone has a genetic tendency toward depression does not mean that person will inevitably become depressed. It may take external events -- the loss of a job, the break-up of a relationship -- to bring depression to the fore.

"There's also evidence, though it's somewhat controversial," adds Jefferson, "that loss in early life predisposes one to depression later in life."

TREATING DEPRESSION

Experts consider Depression the most treatable of any mental disorder they encounter. Between 80% and 90% of people can be successfully treated for clinical depression with antidepressant drugs, psychotherapy, or other treatments such as electroconvulsive therapy. Taking an antidepressant to treat depression is a lot like taking insulin to treat diabetes: it's a way of regulating normal bodily functions when the body can't do the job on its own. A range of antidepressants is available today, and each one of us works a little differently to regulate brain chemistry.

Every antidepressant on the market has undergone careful testing for safety and effectiveness in the treatment of clinical depression. But because each works through different mechanisms, not every medication will work for everyone.

It sometimes takes a while for antidepressants to start working. For some patients, symptoms will start to improve in a week or two. However, it usually takes from 4 to 6 weeks to experience the full effect, and some patients may need even longer. At first, people might notice that they have more energy and are sleeping better. Side effects of the drug (most commonly dry mouth, headache, constipation, dizziness, or trouble sleeping) usually ease after the first month or so.

If no improvement in mood is seen within about 6 weeks, the dose may be too low (which is quite common) or the prescribed medication may not be the best medication for you. The prescribing physician will know how to adjust the dosage and will know when to try a different or additional drug.

Medication is not the only treatment for depression. Individual or group psychotherapy, either alone or in combination with antidepressant medication, is an effective treatment for many people. Studies show that certain kinds of "talk therapy" may be better than others for clinical depression.

Electroconvulsive therapy can also help in major depression, particularly the less common form known as psychotic depression. Most people given electroconvulsive therapy have already tried one or more other treatments, without success.

Support groups, some for depressed people only and some that also include family members, can play an important role in recovery. The nonjudgmental setting of support groups, in which others who have felt the same depths of despair talk about their experiences and share information and advice, is helpful for many people.

THE OUTLOOK

"The road to recovery from depression is a rocky one," write Diane and Robert Hales in Caring for the Mind. Medication may need to be adjusted or changed. It may take several tries to find the right therapist or support group. These setbacks, though, are all part of the process of getting well.

Mental health advocates are working to bring depression out of the closet, and to make people aware of the biological factors that contribute to depression -- and that have nothing to do with willpower, self-control, or attitude.

"The clearest proof that my depression is biological is how well it responds to medication," says Nancy Welch, who now believes she will need antidepressants for the rest of her life. Almost as soon as she started medication in 1993, the darkness lifted -- and it has not returned.

"Within weeks, I was really feeling like I'd made the right choice," Welch says. "My life isn't perfect. But with the right medication at the right dose, huge changes can happen for people. It worked that way for me."

TALKING IT OVER

The following categories are based on definitions in the Diagnostic and Statistical Manual IV, the standard used by psychiatrists and other mental health professionals to diagnose patients.

A depression so severe it interferes substantially with day-to-day functioning. Major depression can last from 2 weeks to years. It usually responds to treatment by psychotherapy, antidepressant medication, or a combination of the two.

A form of depression with fewer symptoms, but which lasts longer -- at least 2 years. Some people find relief from psychotherapy alone, while others require medication as well.

Sufferers alternate between extreme highs and severe depression. These high and low periods can last for days or even weeks. Treatment consists of lithium or other mood-stabilizing drugs plus psychotherapy.

A form of major depression that occurs seasonally, possibly due to changes in available sunlight. Treatment includes psychotherapy, medication, and in some cases, light therapy, which involves spending a prescribed time period exposed to a special light box.

DIAGNOSING DEPRESSION