If, during the winter, you feel blue, gain weight and wake up tired, even though you're sleeping more, you may have seasonal affective disorder.

Seasonal affective disorder, or SAD, is a type of winter depression that affects an estimated half a million people every winter. It is caused by a biochemical imbalance due to the shortening of daylight hours and the lack of sunlight in winter. Ronald Zec, associate professor of neurology and psychiatry at SIU School of Medicine in Springfield, explains the disorder:

SOUND BITE: ". . . this depression has a seasonal pattern. Some of the classical symptoms of clinical depression of being down or blue, depressed and loss of energy. Again, some of the usual features in addition to this regular seasonal pattern is the increased need for sleep rather than insomnia and the hyper phase of appetite carbohydrate weight gain rather than the typical loss of appetite that often accompanies major depression."

Both men and women can have SAD, but is more common in women and it occurs more often in young adults, age 20 to 40. The disorder is more prevalent in the months of December, January and February when the days are shortest. Zec says people who suffer from SAD can be helped by some treatment options. He explains:

SOUND BITE: Probably the most popular treatment, maybe the most effective treatment is the bright light therapy, since the winter depression is due to the decreased photo period - the decreased length of the day, and light deprivation in other words. Bright light . . is what is often prescribed, although antidepressants can also work. Exercise can help in those with a milder form of the the disorder. To some extent, psychotherapy can be a helpful adjunct . . ."

If you or someone you know suffers from seasonal affective disorder and is not helped by bright sun light and exercise, you should see a doctor for evaluation and diagnosis.