Dr. Michael Terman, a professor of clinical psychology at the Columbia University College of Physicians and Surgeons in New York, discusses how to identify and cope with seasonal depression, commonly known as SAD.

Unless you're an avid skier or snowboarder, you probably don't relish the onset of a long winter. For certain people who live in northern climates, the cold, dark days of winter make them feel so sluggish and withdrawn it's hard to get out of bed.

People who start feeling depressed in winter, but experience relief from their symptoms with the buds of spring, may have seasonal affective disorder or SAD. For those who are diagnosed with this condition, light therapy, or other treatments, can restore their energy and alleviate their depression.

What is seasonal affective disorder?

Seasonal affective disorder is characterised by symptoms that start in the fall and snowball in the winter months, and then spontaneously disappear come springtime. It usually starts off with feelings of fatigue, difficulty getting up in the morning, a big afternoon slump and cravings for carbohydrate-rich foods. Coupled with that fatigue, and you have a formula for significant weight gain.

As the symptoms increase, you begin to see depression and a lack of interest in activities. It's difficult to concentrate and get through the day. There's a withdrawal from social contact, including a depressed sex drive, which would be normal during the spring or summer.

One of the classic symptoms is what experts call hypersomnia, where you sleep significantly longer than you sleep in the summer. Hypersomnia is different from person to person, for example if you're a 6-hour sleeper in the summer, you might start sleeping 8 to 9 hours in the winter, and become relatively hypersomnic. But some people will start to sleep 12 or 14 hours a day.

Are there different degrees of SAD?

SAD exists in degrees of severity. Full-blown SAD means literally that you have a clinically severe major depressive episode during the winter. “But many people show the same cluster of physical symptoms and feel only mildly depressed during the winter,” says Terman, “and experts call that sub-SAD.”

Who is at increased risk for SAD?

SAD is widely prevalent throughout the population, and it is worse the farther north you go. In the middle tier of the United States, up to Southern Canada, it's far more prevalent than in the southern states. And most of the people who have SAD have depression in their family.

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