Winter Blues

Every fall, like clockwork, Linda Krentz of Beaverton, Ore., felt her brain go on strike. "I just couldn't get going in the morning," she says. "I'd get depressed and gain 10 lbs. every winter and lose them again in the spring." Then she read about seasonal affective disorder, a form of depression that occurs in autumn and winter, and she saw the light--literally. Every morning now she turns on a specially constructed light box for half an hour and sits in front of it to trick her brain into thinking it's still enjoying those long summer days. It seems to work. "Even my kids notice the difference," she says. "I'm back to my jovial self."

Krentz is not alone. Scientists estimate that 10 million Americans suffer from seasonal depression and 25 million more develop milder versions. But there's never been definitive proof that treatment with very bright lights (10,000 lux, or 20 times as bright as your office lights) makes a difference. After all, it's hard to do a double-blind test when the subjects can see for themselves whether or not the light is on. That's why nobody has ever separated the real effects of light therapy from placebo effects.

Until now. In three separate studies published in the Archives of General Psychiatry last week, researchers report not only that light therapy works better than a placebo but that treatment is usually more effective in the early morning than in the evening. In two of the groups, the placebo problem was resolved by telling patients they were comparing light boxes to a new anti-depressant device that emits negatively charged ions. The third used the timing of light therapy as the control.

Why does light therapy work? No one really knows. "Our research suggests it has something to do with shifting the body's internal clock," says Dr. Al Lewey, a psychiatrist at Oregon Health Sciences University in Portland. The body is programmed to start the day with sunrise, Lewey explains, and this gets later as the days get shorter. But why such subtle shifts make some people melancholy and not others is a mystery.

That hasn't stopped thousands of winter depressives from trying to heal themselves. Light boxes for that purpose are available for $300 to $600 without a doctor's prescription. That bothers Michael Terman, a research psychologist at Columbia University. He is worried that the boxes may be tried by patients who are suicidal or suffer from mental illness that can't be treated with light. Terman has developed a questionnaire, available at www.cet.org/cet2000, to help determine whether you should seek expert care.

In any event, you shouldn't treat yourself without doing your homework. Start by reading Winter Blues by Dr. Norman Rosenthal (Guilford Press), and then choose a reputable manufacturer, like the SunBox Co. of Gaithersburg, Md. www.sunboxco.com), or Enviro-Med of Vancouver, Wash. www.teleport.com/~biolight/). Whatever product you use should emit only visible light, because ultraviolet light damages the eyes. If you are photosensitive, you may develop a rash if you're taking certain medications, including sulfa drugs. Otherwise, the main drawback is having to sit in front of the light for 30 minutes to 60 minutes first thing in the morning. That's an inconvenience many winter depressives can live with.

For more on treating seasonal depression, see time.com/personal. You can e-mail Christine at gorman@time.com.