Winter depression

It’s been an unseasonably warm October here in the northeast, so it is hard for me to imagine that winter is coming soon. But it is, and some of us will be taking it hard.

A sunny disposition is by definition a happy one, and a wintry atmosphere is cheerless. For 1 or 2 out of 100 people, winter sluggishness and gloom take the form of clinical depression. In the 1980s, this condition was given the name of seasonal affective disorder (SAD), and researchers have since learned that bright light is often an effective treatment.

Seasonal affective disorder is defined as depression that occurs repeatedly at the same time of year, usually starting in fall and ending in spring. Winter depression accounts for about 10% of cases of major depression. It appears to run in families, and twin studies suggest that there is a hereditary disposition to seasonal mood change.

Let there be light

Sunlight has always been regarded as an antidote to lethargy and gloom, and now the effect of bright light treatment on seasonal mood change may also be evidence for the circadian rhythm theory of winter depression. Fluorescent lights are mounted on a metal reflector, with a plastic screen that filters out damaging ultraviolet frequencies and diffuses the light to prevent glare. The box containing the apparatus sits on a stand or tabletop, and the patient sits nearby for a half-hour to two hours a day. Lights can also be attached to a visor worn on the forehead.

Using a standard measure of brightness, experts usually recommend about 10,000 lux, which is more or less equivalent to early morning sunlight. It is not necessary to match the exact color spectrum of visible sunlight — ordinary fluorescent lights are adequate. Morning light is usually preferred, because it is supposed to reset the body’s clock by moving internal cycles forward and synchronizing them with the rhythm of daylight and darkness. That is also the function of another device, the dawn simulator, a bedside timer that gradually increases bedroom light in the morning to create an artificial early dawn.

Improvement begins in a few days, and treatment continues throughout the winter. There are few side effects, mainly occasional headaches or eyestrain. Sometimes a patient with bipolar disorder may develop mania.

The cost is usually covered by insurance. For milder seasonal mood changes, adding more lamps, sitting near windows, or spending more time outdoors may help. One study found that an hour’s walk in winter sunlight was as effective as 2 1/2 hours of artificial light — and the patients were also getting exercise.

Other approaches

Antidepressant drugs, chiefly the selective serotonin reuptake inhibitors fluoxetine (Prozac), sertraline (Zoloft), and citalopram (Celexa) have been found effective for winter depression in controlled trials. (Serotonin is one of the neurotransmitters in the pathway that runs from the brain’s pacemaker to the retina, and the body makes melatonin from serotonin.) The herbal St. John’s wort also seems to help. Melatonin, although it may relieve symptoms of jet lag, has not been proved to be an effective treatment for seasonal affective disorder when taken alone. A few studies suggest that it may be useful when taken in the evening in combination with morning light therapy. Patients with seasonal mood changes may also benefit from cognitive behavioral therapy. One four-month controlled trial found that group cognitive behavioral therapy, bright light, and a combination of the two were all equally effective.

Many unanswered questions about seasonal mood change remain. For example, studies in Iceland and northern Russia suggest that winter depression is less common in Europe than in North America. Maybe climate, culture, and professional diagnostic practices have to be considered as well as changes in sunlight. Research on seasonal mood change should also provide insight into other problems associated with physiological cycles, such as the effects of night work and jet lag.

How does the change in seasons affect you? If the darker months are tougher for you, have you found anything that helps you bear up?

Dr. Michael Miller has been on staff of the Beth Israel Deaconess Medical Center, a large teaching hospital in Boston, for more than 25 years. He is also an Assistant Professor of Psychiatry at Harvard Medical School.

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