BODY WATCH : Light Therapy : Anyone can suffer depression from lack of sunlight. But quality time with a fluorescent fixture can cure it.

Of constitutions some are well or ill adapted to summer, others are well or ill adapted to winter. --Hippocrates

Several years ago when Army psychiatrist Dr. Matthew E. Levine was transferred to the northern Alaska outpost at Ft. Wainwright, he noticed a common complaint among his patients.

During the long nights of winter, many of those who sought his help were suffering from severe depression. And when winter finally gave way to summer, with more than 20 hours of sunlight, the depression disappeared.

His patients all had similar complaints: They ate too much, had little energy, were irritable and had almost no interest in sex. In many cases, they had one other common symptom: a growing dependence on alcohol.

Levine teamed up with scientists at the University of Alaska’s Institute of Arctic Biology and carried out key research into a phenomenon that has been recognized only in recent years as a serious medical problem. Seasonal affective disorder--SAD, for short--is an extreme case of the winter blues, and it strikes people of all age groups, especially women.

SAD is different from other forms of depression in that it strikes only in the winter, or late fall, and it clears up in the spring. And it affects people who have no previous record of depression.

What makes Levine’s work particularly significant is that it was carried out in the extreme north, near the tip of the North American continent. SAD is a far more serious problem at more northern latitudes than it is farther south, although it can strike even in Southern California.

University of Alaska chemist Lawrence K. Duffy, who headed the university’s part of the research, studied soldiers and their dependents at Ft. Wainwright, as well as native Alaskan residents of northern villages. The results reveal that melatonin, a chemical produced by the body’s pineal gland and known as the “hormone of darkness,” probably plays a key role in bringing about winter depression. The findings may also have important implications for another malady plaguing Alaska: alcoholism.

“We feel that melatonin levels are intimately involved” in SAD, and possibly alcoholism, Duffy said. “What we see up here is a broadening of the melatonin level because of the reduced amount of light. You just have higher levels” at more northern latitudes, apparently because of the deprivation of light.

Whether it is the melatonin--or simply the lack of light--that causes the depression remains to be proved, Duffy said.

Levine and Duffy believe that their results confirm the earlier pioneering research of Dr. Norman E. Rosenthal, a psychiatrist with the National Institute of Mental Health, which suggested that simply exposing patients to bright light each day for about a week is the best treatment. Light lowers the level of melatonin.

Many psychiatrists favor mood-elevating drugs, but Levine said his work showed that light worked at least as well, and it was a lot cheaper.

“Many psychiatrists are more comfortable using medication,” Levine said. “They use it for everything else.”

Having a patient sit down in front of a fluorescent light box for an hour or two each day is “just too simple of a solution.”

Yet he found an even simpler treatment.

“All you really have to do is get out for a half hour to an hour in the middle of the day, even if it’s not a sunny day,” he said. That will provide ample light to clear the winter blues.

But in places like the far north, people are less inclined to do that because daylight lasts only about three hours in the winter, and it is very cold.

“But if you go out and take a walk for half an hour you won’t freeze to death if you bundle up,” he said.

In addition to its now widespread use to treat SAD, light-box therapy is now increasingly used to help shift workers change their circadian rhythms so they can sleep in the daytime; it is also used to assist travelers in overcoming jet lag.

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Statistics suggest that SAD affects women more than men by a ratio of about 3 to 1, a fact that has puzzled some researchers. It could be that more women are inclined to stay inside during the winter months, particularly in the tradition-bound villages of the north, but Levine sees another reason as well.

“Women are more sensitive to biorhythms than men,” and the production of melatonin, which occurs when the body adjusts to the nighttime, is part of that biorhythm process, he said. “Women’s bodily rhythms are very pronounced over a month’s time. . . . The light seems to disrupt the female reproductive rhythms more than it does in men.”

That is known to be the case among females of one species, but Levine said he hesitated to bring it up because some women might find it offensive.

“Poultry farmers put the lights on in the chicken coop,” he said. The light “increases the number of eggs that the hen lays. So it’s well known that light has a very strong effect on female physiology, at least for hens.”

The team’s research also suggests that melatonin might play a significant role in alcoholism. The hormone reduces sleep, leading to fatigue, two factors that seem to contribute to alcohol abuse. Studies involving the homeless in Fairbanks, Alaska, for example, showed that more than two-thirds drank at “either a highly intoxicated level or at a severely intoxicated level,” and many suffered from symptoms consistent with SAD.

The problem is especially serious for the Alaskan natives who live in remote villages of the far north. Researchers from Pennsylvania State University and the Hershey Medical Center found last year that the suicide rate for Alaskan natives was twice the national average. The most common psychiatric disorder among the victims was alcohol abuse, leading the researchers to conclude that alcoholism was “the most important antecedent of suicide” among those studied.

Duffy is planning other research projects into the reduction of melatonin--and possibly light treatment--as an aide in treating alcoholics.

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Oddly enough, the Alaskan natives who live on the northern edge of the state have developed no immunity to SAD, despite the fact that they have had to deal with the long nights for many, many generations. Yet research carried out by scientists from the National University Hospital in Reykjavik, Iceland, shows that Icelanders appear to have developed such immunity--recent generations are far less likely to suffer from the affliction than others living at similar latitudes in North America.

Research in other northern-latitude settings has further expanded the understanding of SAD.

Scientists in The Netherlands found that giving light treatment at the first signs of the winter blues appears to prevent it from developing into a full-blown depression. The researchers reported last year that “not a single patient from a group of 16 treated this way became severely depressed during the remaining part of the winter season,” whereas five of 11 who were not treated came down with SAD.

Those same researchers tried to nail down the time of day when the treatment works best, and they came up with another surprise: It made no difference if the light treatment was given in the morning or in the evening. Other researchers have found similar results. A team from Switzerland concluded that “time of day is not crucial” for the light treatment to be effective.

Most researchers, including the Alaskan team, favor the use of bright lights consisting of several fluorescent tubes, but researchers at the University of Toronto found no significant difference “in antidepressant efficacy” of lights ranging from mild to intense.

The color of the light does seem to make a difference, however. Researchers at Jefferson Medical College in Philadelphia found that green light did not work as well as white light, leading them to conclude that “broad band white light (sometimes called full spectrum) may be optimal for maximizing therapeutic response.”

There seems to be no debate over whether that light treatment does in fact work for SAD. A survey of 159 research papers from around the world found not a single challenge to that finding. But there is no evidence it works for any other form of depression.

What remains to be determined is why it works for SAD.

If it is because the absence of light increases the level of melatonin, as Duffy believes, and melatonin causes the depression, then researchers may have found a tool that could be helpful in the treatment of afflictions ranging from SAD to alcoholism.