Could You Have Seasonal Affective Disorder?

It's normal to feel a little down this time of year, when chilly temps force you to finally haul out your parka from storage and the disappearing afternoon sun guarantees a dark commute home. But if inching closer to winter has plunged you into a serious funk you can't shake, you might be dealing with something more than a blah mood.

Seasonal Affective Disorder (SAD) is a type of depression that can occur at the change of any season. Yet it often emerges at the end of daylight savings time, when reduced exposure to energy- and mood-boosting sunlight triggers changes in brain chemistry that in some people leads to profound sadness. "People with SAD feel so despairing, it affects their ability to function," says Jennifer Wolkin, Ph.D., clinical assistant professor of psychology at the Joan H. Tisch Center for Women's Health at NYU Langone Medical Center.

So how can you tell if your spirits are a little down because bikini season is more than six months away, or you're facing SAD? Go through this checklist. If at least two describe you, see your doctor, who will screen you and may prescribe meds or light therapy as treatment.

1. Since autumn, you've been gripped by sadness. As temperatures continue to cool and the sun sets earlier-and you don't have the same sunlight fix you're used to in spring, summer, and early fall-your moods are increasingly darker.

2. Your low mood lasts more than two weeks. While a regular case of the blues hits the road after a few days, SAD, like other forms of depression, persists, says Wolkin.

3. Your day-to-day life is taking a hit. Feeling down in the dumps wouldn't prevent you from getting out of bed in the morning, right? "SAD, however, causes a depression so intense, it keeps you from functioning normally in your job and relationships," says Wolkin.

4. Your lifestyle habits have changed. SAD casts a dark shadow on energy level, appetite, and sleep routine-making you more likely to skip the gym, eat more or less, and have difficulty getting quality shuteye or even oversleeping.

5. You've isolated yourself. "People with clinical depression feel so off, they're less likely to see friends and family or derive joy from the activities they used to take part in, so they skip them," says Wolkin. The more you self-isolate, however, the more depression intensifies.