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Winter depression: rise and shine?

Winter depression: Rise and Shine?

As daylight wanes in the fall and winter,some people slow down, oversleep, over-eat and become depressed and unable to function normally. In a number of studies, artificial bright lights have eased these symptoms of winter depression, also known as seasonal affective disorder (SAD) (SN: 3/9/85, p.152).

Yet reports from several laboratoriespresented last week failed to resolve a key question: How do the lights work?

At the meeting of the American Collegeof Neuropsychopharmacology in Washington, D.C., Alfred J. Lewy and Robert L. Sack of the Oregon Health Sciences University in Portland reported that the daily biological rhythms of most winter depressives are delayed and appear to be reset by morning light, which they find to be the best treatment for SAD. In a study of 19 such patients, the researchers used the hormone melatonin as a marker for light sensitivity and body rhythms.

Melatonin secretion begins when it becomesdark, gradually reaches a peak during the night and falls again with the approach of daylight; in 18 of the patients, this pattern began and ended several hours later than normal. These patients markedly improved over four weeks when exposed to one-half hour or two hours of bright light upon awakening in the morning; light presentation from 8 p.m. to 10 p.m. was far less effective, and a combination of morning and evening light resulted in improvement about half-way between morning-only and evening-only conditions.

"It is as if the light exposures whengiven together counteract one another," says Lewy.

The exceptions included one subjectwho responded worst to morning light and best to evening light, notes Lewy, and had a melatonin secretion pattern that was advanced, rather than delayed, by several hours. In addition, about one-quarter of the patients responding to morning treatment did better on one-half hour of light than on two hours of light.

"'The more bright light the better' isnot necessarily the case for SAD patients," says Lewy. "By and large, most of them are phase delayed [with respect to daily biological rhythms] and should respond preferentially to morning light." But it is difficult, he adds, to control for nonspecific effects, such as patient expectations, in light treatment studies.

Support for Lewy's hypothesis comesfrom a study conducted by Frederic Quitkin and his colleagues at the New York State Psychiatric Institute in New York City. They observed the most substantial improvement among 28 SAD patients exposed for one week to two hours of bright light in the morning and evening; significant improvement also occurred with two hours of morning light only and 30 minutes of morning and evening light. Evening light treatment alone produced negligible effects.

"There were complete remissions onlyamong patients who got at least some morning light," says Quitkin.

Other researchers contend, however,that the brightness and duration of light is more important than its timing. In a study conducted by Norman Rosenthal and his colleagues at the National Institute of Mental Health (NIMH), two hours of bright light at midday were as effective as two hours in the morning among 16 SAD patients. Previous studies, notes Rosenthal, have found even greater improvement among winter depressives exposed to four hours of evening light, from 6 p.m. to 10 p.m.

"Most SAD patients seem to be moresensitive to morning light treatment," says Rosenthal, "but since you can get the same effects at other times, a resetting of biological rhythms is probably not taking place." Bright lights, he suggests, may temporarily correct an as-yet-unidentified chemical imbalance in the brains of SAD patients.

Most winter depressives examined atNIMH ride a seasonal pendulum, becoming agitated, gregarious and impulsive in the spring and summer (SN: 3/8/86, p.152). But Lewy observed no such symptoms among 40 SAD patients in Portland. Long, bright summer days are less frequent in the Pacific Northwest, says Rosenthal, and may account for the lack of a seasonal swing there.
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Title Annotation:morning light found to be best treatment for seasonal affective disorder
Author:Bower, Bruce
Publication:Science News
Date:Dec 20, 1986
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