"SAD is thought to be related to a chemical imbalance in the brain brought on by lack of light due to winter's shorter days and typically overcast skies," says Dr. Angelos Halaris, chief of the psychiatry and behavioral sciences department at Loyola University Health System.

As many as 10 percent to 20 percent of Americans may experience a mild form of SAD, according to the American Psychiatric Association. Certain people may have a genetic vulnerability to developing the condition, which affects more women than men and tends to start appearing in the teen years.

"This condition, characterized by depression, exhaustion and lack of interest in people and regular activities, interferes with a person's outlook on life and ability to function properly," Halaris said.

You can take steps to reduce the risk of developing SAD.

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Scientists from France have found that anorexia and the highly addicting club-drug ecstasy activate some of the same brain pathways, a finding that may help explain the addictive nature of anorexia and other eating disorders and lead to new treatments.

In a paper published this week, Dr. Valerie Compan of Centre National de la Recherche Scientifique, Montpellier, and colleagues report that both anorexia and ecstasy reduce the drive to eat by stimulating the same subset of receptors for the neurotransmitter serotonin.

These so-called 5-HT4 receptors are located in a brain structure associated with feelings of reward called the nucleus accumbens.

In mice, Compan and colleagues stimulated these receptors, which are known to play a role in addictive behavior, and found that this led to anorexic-like behavior -- food-fed mice ate less and food-deprived mice showed a reduced drive to eat.

"It is alarming to see that there is still a fear regarding antidepressant use during pregnancy. We knew that some women were going to discontinue using their antidepressants during pregnancy but we didn't think it would be so prevalent and inappropriately used (amongst those who remain on it)," senior author Dr. Anick Berard told Reuters Health.

"The risks of untreated depression during pregnancy are significant," Berard, from the CHU Sainte-Justine Hospital in Montreal, said. "Given the safety of most antidepressants during pregnancy, a careful evaluation of the risk/benefit ratio should be done before deciding to discontinue their use. Although physicians and women think they are protecting their unborn child, they might be doing just the contrary."

People who feel chronically stressed on the job may face an increased risk of depression, a large study suggests.

Researchers found that among more than 24,000 working Canadian adults, nearly 5 percent had suffered from major depression in the past year. Those under heavy stress at work appeared to be at particular risk, according to findings in the American Journal of Public Health.

A number of studies have found health risks associated with chronic job stress, including high blood pressure and heart disease, as well as depression. However, the depression studies have been limited to either certain occupations or single companies, noted Dr. Emma Robertson Blackmore, the lead author of the new study and an assistant professor of psychiatry at the University of Rochester Medical School in New York.