Seasonal affective disorder

Nobody (nobody human, anyway) likes getting up on a cold winter’s day when it’s still dark and the wind is howling, but for some people it’s more than just unpleasant: it’s almost impossible. They suffer from a form of depression called Seasonal Affective Disorder (also known, appropriately, as SAD).

Seasonal depression has probably been around forever, but it’s only recently been recognized as a legitimate medical problem. It’s not easy to diagnose, either; although many people–as many as one in four–suffer from “the winter blues” (a.k.a. sub-syndromal SAD), a person can only be diagnosed as having SAD if he or she suffers three or more consecutive winters of some (or all) of: sleep problems (usually difficulty staying awake, but sometimes difficulty getting a sound sleep and a tendency to wake up too early), lethargy, overeating (caused by a craving for carbohydrates), depression, social problems (irritability and a desire to avoid people), anxiety, decreased interest in sex and, sometimes, mood swings and, in the spring or autumn, three or four weeks of excessive activity. Most people suffering with SAD also show signs of a weakened immune system in the winter, which makes them more vulnerable to infections and other illnesses.

SAD may begin at any age, but it most commonly manifests itself between 18 and 30, and it tends to run in families. It’s very rare in people living within 30 degrees of the equator; in general, it becomes more common the further north you go. That’s because SAD appears to be caused, through some mechanism that yet understood, by a lack of light.

We know that because of research pioneered by Dr. Norman E. Rosenthal, Chief of the Section of Environmental Psychiatry at the U.S.’s National Institute of Mental Health. When Dr. Rosenthal moved from his native South Africa to New York to begin his psychiatric residency, he experienced short winter days for the first time, and soon found himself feeling tired, sluggish and overwhelmed by everything he had to do. The mood lifted in the spring, but left him puzzled.

When Dr. Rosenthal went on to complete his residency at NIMH in the early 1980s he met Herb Kern, a research scientist with a background in engineering, who had noticed a pronounced seasonal swing in his own mood and theorized that it might be due to a lack of sunlight. He’d contacted NIMH to see if it would be interested in researching his idea, and Dr. Rosenthal decided to follow up on it.

What he found is that SAD can usually be alleviated by exposing the sufferer to an amount of light similar to what he or she would receive during the summer. The researchers exposed Mr. Kern to three hours of bright light in the morning and the evening, and his overall mood improved after just three days. Further research has shown that “light therapy” is effective in treating 85 percent of SAD sufferers.

Light therapy consists of sitting less than a metre away from a specially designed “light box” that allows bright light–at least 10 times as bright as ordinary domestic lighting–to shine directly into your eyes. It’s not necessary to stare directly into the lights; just sitting there reading or doing something else and occasionally glancing up is enough to garner the benefits.

A light box, alas, isn’t something you can whip up in your own workshop. Too little light does no good, and too much can cause eye damage, and the precise amount of time needed in front of the light box varies greatly from person to person and changes as the seasons progress, ranging from as little as 40 minutes per day to several hours, combined with psychotherapy and anti-depressant drugs such as Prozac and Zoloft.

These drugs’ effectiveness supports a theory that in some people a change in the level of light they’re exposed to makes it difficult for their brains to regulate the level of a soothing chemical called serotonin. The craving for carbohydrates common to SAD sufferers also supports that theory: eating foods rich in carbohydrates temporarily increases serotonin levels.

So if winter is too much for you to bear, talk to a doctor who’s familiar with SAD. Nobody likes cold weather, shoveling snow, and getting up in the dark, but most of us cope. If you can’t, just a little extra light in your life might help lift the gloom.

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