问答题 《复合题被拆开情况》 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【S1】__________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【S2】________light box for half an hour and sit in front of it to trick her brain into【S3】________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.【S4】________But there’s never been definitive proof which treatment with very bright【S5】________lights makes a difference. In all, it’s hard to do a double-blind test when【S6】________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【S7】________placebo effects. Until now, in three separate studies publishing last month,【S8】________researchers report not only that light therapy works better than a placebo and that treatment is usually more effective in the early morning than in【S9】________the evening. In two of the groups, the placebo problem was resolved by telling patients what they were comparing light boxes to a new anti-【S10】________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.《问题》：【S3】