To some, it's a myth; to others, it's an annual plight. Seasonal Affective Disorder is not yet fully understood -- but as days grow shorter, sufferers report symptoms like less energy, sleepiness, increased appetite and sadness. Metro asked psychologist Dr. Janis Anderson, the director of Boston's Brigham and Women's Hospital's Seasonal Affective Disorders Clinic, for some insight into this peculiar problem.

What is Seasonal Affective Disorder?

Seasonal Affective Disorder is a form of major depression. The timing is different, but the presentation is the same. Major depression is depression lasting longer than two weeks that interferes with normal life.

Isn't S.A.D. just a myth?

We've seen brain scans and studies that have shown that Seasonal Affective Disorder fits the major depression profile. There are physiological changes that are the same.

Does our vitamin D production have something to do with it?

Some studies have looked into that, and there's some speculation. But there is no specific evidence. The evidence points to daylight hitting the retina, which in turn affects parts of the brain that respond to light, even in blind people. Mammals [use an] internal calendar.

Do we know what causes it?

There were studies done in Alaska and Siberia that compared natives who still lived a traditional life with those who led modern city lives. The rates of S.A.D. were higher in the people who lived modern lives. We don't know why. It's one of those intriguing mysteries.

Is it preventable?

Move to Hawaii! Really, it's sensitive to geographical location. The further from the equator, the more incidences we see.

How can it be treated?

We see improved function with more light exposure. Walking in daylight without sunglasses, even if it's cloudy, for 40 minutes a day, helps -- particularly in the early morning hours.

Who gets S.A.D. more, men or women?

“Women. We just don’t know why. It’s true that in general women have more depression. But it’s certainly true of S.A.D.”

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