Every year with the first frost, Carl Harris' mood would plunge into deep freeze. Normally a man of sunny disposition, he would turn as lethargic and grumpy as a hibernating grizzly. As the winter progressed, he would alienate family and friends with his snappish-ness and add ten unwanted pounds by overeating at meals and indulging any sudden craving for sweets. The only thing that would lift Harris out of this slough of winter despond was a visit to the plant-growth research center run by his former employer, the U.S. Department of Agriculture. He would stand in the lab among the plants and bask in the glow of bright fluorescent lights. "I would step into a growth chamber and just get this charge," he says. "I loved horticulture and plants, so I thought that it was just from all the flowers."

Today Harris knows that his seasonal slumps are a severe form of the winter blahs. He has also learned that it wasn't the flowers, but the fluorescence, that was lightening his mood. Harris is one of more than 300 patients who have been treated by National Institute of Mental Health psychiatrist Dr. Norman Rosenthal for Seasonal Affective Disorder—known as SAD—a cyclical mood-shift syndrome that afflicts an estimated one million Americans, though many remain in the dark about their malady. SAD has been recognized since 1984 as a distinct form of depression, thanks in part to Rosenthal's efforts. Rosenthal was the first to pinpoint the major symptoms—lethargy, overeating—that distinguish SAD from other types of depression, which frequently cause sleeplessness and loss of appetite. But the most striking feature of SAD, he found, is not the symptoms but the apparent cure: full-spectrum light.

A native of South Africa, Rosenthal moved to New York City in 1976 for a residency at Columbia Presbyterian Medical Center. He found himself sluggish and out of sorts during the harsh U.S. winters, and in 1979 he joined a group at NIMH that was studying the connection between circadian rhythms—the body's internal time clock—and manic-depressive illness. It was this group's work, investigating possible links between light and hormone levels in the brain, that led Rosenthal to postulate that some forms of depression might be seasonal—and treatable with bright lights. In 1981, when the Washington Post ran an article about Rosenthal's SAD studies that asked for research volunteers, thousands responded. Among those Rosenthal has since treated with phototherapy—or regular doses of light—80 percent have responded favorably. Says Rosenthal: "This light is correcting a chemical imbalance in patients' brains that is manifest only when the amount of light they are naturally exposed to decreases."

Among the beneficiaries of Rosenthal's research is Dalene Barry, a 44-year-old writer from Washington, D.C., who had been miserable every winter for 30 years before she read about his work. Come November, she says, "I'd feel lethargic, old and heavy. I felt like I couldn't think and didn't have anything to say to anybody." Like Harris, she would become obsessed with eating, putting on as much as 30 to 40 pounds. By spring, though, Barry would start slimming down and zipping along on only four hours of sleep a night. When she heard about light therapy, Barry says, "I thought it was a little bizarre, but I liked the idea that you didn't have to ingest anything." After only a few days of light treatment, Barry was given an exercise bike to burn off her excess energy. She gave away all the sweets she had and tore through a pile of work. "It was as if I'd been freed," she says.

The key to the onset of SAD, Rosenthal has found, is not how much light hits the skin, but how much enters the eye. Visits to a tanning salon won't help, nor will quick trips to the Caribbean. The only effective treatment, according to Rosenthal, seems to be full-spectrum light administered in regular daily doses. To fill that need, Neal Owens, a SAD sufferer who heard about Dr. Rosenthal's methods in 1985, quit his job with a petroleum company to begin manufacturing specialized light boxes that sell for about $400 apiece. (A Boston psychiatrist, Dr. Martin Teicher, claims he gets the same results for $30 by mounting two 150-watt Spot-Gro Sylvania bulbs in front of a reflector.) Owens' specially made box provides about the same illumination a person would receive while standing at a window on a bright spring day. These days Carl Harris puts his in the family room of his home in Takoma Park, Md., and rises early to sit before it and read for two hours. "You wish you could carry these boxes around like an umbrella," he says. "They're like your babies. You love them." In fact, as Owens discovered, the boxes can become addictive. "I started using them for two hours a day, and it was like drinking coffee," he says. "My mind just started racing, and I had to cut down."

Rosenthal speculates that the propensity to SAD may be an evolutionary holdover from the time when bulking up and slowing down helped cave men and women survive the lean winter months. But he cautions against seeing phototherapy as a panacea. In fact, other researchers have recently found evidence of a reverse SAD syndrome, in which the onset of warmer summer weather can trigger depression. "People can be depressed for all kinds of reasons," notes Rosenthal. But for the truly SAD-afflicted, his work has pierced the gloom like a bright ray of sunshine.

  • Contributors:
  • Susan Schindehette.