Seasonal affective disorder

Let the sun shine in when it's dark outside.

Published January 3, 2000 5:00PM (EST)

Down in the dumps? Want to curl up in bed rather than go hang gliding? Are you eating lots of candy and fruitcake? Gaining weight? You bet: It's cold and dark out.

More than just a season, winter has become a metaphor for the dark side of life. Most of us accept the winter blahs as normal and wait for spring. But for some, seasonal doldrums can be a real problem.

My mother, a tradition-confused West Coast Jew, might have been onto something. She insisted on having a large Christmas tree in the living room, but she refused the usual panoply of ghastly colors. Instead she used exclusively white bulbs. "Colored lights are for the goyim," she would say with the slyest of smiles. When pressed, she would add, "Bright white is better for your spirits." (Another Jewish tradition -- justifying any peculiar taste on the basis of health reasons).

But was my mother right? Were the bright white Christmas tree bulbs therapeutic? Would votive candles have done the job? Or a trip to Florida? Or spending the winter in a brightly lit casino? Are TV and computer monitors evolutionary answers for the winter blahs? I don't doubt that we get bummed out at this time of year, but is this a specific biological condition or a more metaphysical malaise?

In the late 1970s a South African psychiatrist, Norman Rosenthal, first correlated winter depression with decreased exposure to light. After moving to New York in the dead of winter to begin his psychiatric residency, Rosenthal felt tired, sluggish and overwhelmed by his work schedule. When spring arrived, his mood lifted; he felt renewed and energized. The obvious explanation (especially for a shrink) was the change in latitude -- the shorter days, longer nights. Rosenthal blamed his depression on dim lights, not the big city.

He decided to test his theory. At the National Institutes of Mental Health he exposed subjects with a history of winter depression to several hours a day of artificial light. Many reported improvement in their symptoms. In the early 1980s, after his tests, the term "seasonal affective disorder" (SAD) was coined.

Symptoms of SAD are very similar to those of non-seasonal clinical
depression: change in appetite, weight gain, drop in energy, tendency to oversleep, difficulty with concentration and irritability. The key factor in diagnosing SAD, though, is its seasonal pattern: The above symptoms fade away with the arrival of spring and return in the fall.

Curiously, the single physical symptom that seems to correlate best with SAD is the strong craving for sweets. Rosenthal and others theorize that people with SAD have difficulty in regulating
serotonin levels during the winter and that their craving for carbohydrates is a way of compensating. (Carbohydrates are believed to increase the level of the neurotransmitter serotonin, and lower-than-normal levels of serotonin are correlated with clinical depression.) Perhaps this is the evolutionary rationale behind those dreadful fruitcakes.

This theory also explains why many SAD patients respond favorably to selective serotonin reuptake inhibitor (SSRI) antidepressants such as Prozac or Zoloft. Other researchers postulate a disturbance in circadian rhythms -- an alteration in the biological clock that affects serotonin metabolism. (Perhaps we were meant to hibernate in winter.) Though antidepressants are of value, the cornerstone of treatment for SAD is light therapy.

Light therapy comes in all sizes, colors and intensities. Although
Rosenthal's original experiments used full-spectrum fluorescent tubes, his later research showed that light from incandescent and
halogen bulbs was just as effective. No one bulb is definitely better than another. Even intensity may not matter. Amount of exposure time is also unclear. Despite a lack of evidence for superiority
of any specific light source, the standard seems to be full-spectrum non-ultraviolet fluorescent tubes because of their even disbursement of light and cool operating temperatures.

A typical treatment strategy begins with having the patient set up a light box on a table to sit directly in front of while eating breakfast or reading the newspaper. Exercise is also a critical element of treatment. Dr. Rosenthal suggests taking a quick walk during lunch breaks. Even on overcast days, the sunlight filtering through the clouds is beneficial. In the evenings the patient can have another session in front of the light box, perhaps while eating dinner. (Estimates as to optimal exposure vary; some say that 60 to 80 percent of patients feel better with as little as 30 minutes under the lamp.)

It's not necessary, or even recommended, to stare into the light.
The entire retina responds to light, so it's possible to get the full
benefit of light therapy while reading, talking on the phone or even watching television.

I have friends who swear by the light treatment. I personally feel better on sunny days. But how specific is SAD? Is it a discrete disorder, or merely an extension of ordinary depression? I hear "Jingle Bells" or "Rudolph the Red-Nosed Reindeer" and I look around for a sharp knife, a nice comforting loop of rope, a plastic bag inscribed "Here lies a man who detested the holiday season." I doubt that standing in front of a searchlight would make a difference. Even the constitutionally euphoric get depressed when double-parked in standstill traffic while the spouse runs in
to a jam-packed mall to exchange that scratchy purple sweater from your aunt in Toledo.

Fifteen years have passed since Rosenthal's original paper, but I'm still a bit in the dark about SAD. If the disorder is related to diminution in light exposure, shouldn't the prevalence of SAD be greater at higher latitudes? Some studies say yes, others show no difference. And some Northerners (Icelanders in particular) appear peculiarly immune to the disorder. Does this negate the light hypothesis or merely point to other complicating factors such as genetically influenced decreased susceptibility to depression? That was Rosenthal's speculation -- but no one knows for sure.

The issues of duration and intensity of light exposure remain unanswered. Rosenthal now believes that light intensity may not be an issue -- in fact levels as low as those mimicking the beginning of dawn can be therapeutically effective. And there is the problem of assessing light therapy against a placebo. I cannot imagine what would be used as a non-light source placebo.

So we are left with a common-sense observation that lack of light seems to cause depression in winter. Science has provided some tantalizing clues but no final answer; there's more to darkness than meets the eye. In the meantime, keep warm, exercise (preferably outdoors), eat sensibly and, above all, keep well lit.

By Robert Burton

Robert Burton M.D. is the former chief of neurology at Mount Zion-UCSF Hospital and the author of "On Being Certain: Believing You Are Right Even When You're Not" and "A Skeptic's Guide to the Mind." A former columnist for Salon, he has also been published in the New York Times, Aeon and Nautilus, and currently writes a column at the Cambridge Quarterly for Healthcare Ethics.

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