Every fall, like clockwork, Linda Krentz of Beaverton, Oregon,

felt her brain go on strike. “I just couldn’t get going in the morning,”

she says. “I’d get depressed and gain 10 pounds every winter and lose it 【M1】________

again in 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 in a specially constructed 【M2】________

light box for half an hour and sit in front of it to trick her brain into 【M3】________

thinking it’s still enjoying those long summer days. It seems to work.

Krentz is not alone. Scientists estimate that 10 million Americans

suffer seasonal depression and 25 million more develop milder versions. 【M4】_________

But there’s never been definitive proof which treatment with very bright 【M5】_________

lights makes a difference. In all, it’s hard to do a double-blind test when 【M6】_________

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 with 【M7】_________

placebo effects.

Until now, in three separate studies publishing last month, 【M8】_________

researchers report not only that light therapy works better than a

placebo and that treatment is usually more effective in the early morning 【M9】_________

than in the evening. In two of the groups, the placebo problem was

resolved by telling patients what they were comparing light boxes to a 【M10】________

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 psychiatrist Dr. Lewey.

【M8】