Winter Depression

The treatment of seasonal affective disorder throws light on dark moods

For one 1 or 2 out of 100 people, winter sluggishness and gloom take the form of clinical depression. In the 1980’s 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. The American Psychiatric Association’s official definition requires a lifetime of mostly winter depressions, including at least two straight years without any episodes out of the winter season.

People with seasonal affective disorder are sad, tired, anxious, irritable, unable to concentrate, inclined to avoid friends and social activities – all typical symptoms of depression. But sometimes they have atypical symptoms: overeating, and excessive sleep. Winter depression accounts for about 10% of cases of major depression. It appears to run in families, and twin studies suggest there is a hereditary disposition to seasonal mood change.

According to a popular theory, the phase shift theory, the internal body clock does not adjust to later dawns and earlier sunsets in people with seasonal affective disorder. The same phenomenon causes jet lag in travelers, and affects night workers who must stay awake while the world is asleep. People with seasonal affective disorder, according to this theory, are arising at a time when their bodies insist on sleep, with unfortunate affects on mood and energy. Some patients with the disorder say they feel as though they could hibernate.

However, the more circadian cycles (the 24-hour body rhythms) are investigated, the more complicated they look. Experiments have shown that the cycles persist, even in people who are not exposed to changes in daylight. And, it’s been found that the activity in many individual cells, both in the brain, and in various tissues, has a 24-hour rhythm. These are controlled by the cells’ own genes and respond to external signals independent of the brain.

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. In this treatment, fluorescent lights are mounted on a metal reflector, with a plastic screen that filters out damaging ultraviolet frequencies. The box containing the apparatus sits on a stand or tabletop, and the patient sits nearby for a half-hour to two hours per day. There is also another device, called a dawn simulator, a bedside timer that gradually increases bedroom light in the morning to create an artificial early dawn.

Experts recommend light intensity of 10,000 lux, which is more or less equivalent to early morning sunlight. 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.

Usually, 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 American Psychiatric Association’s annual meeting concluded, after reviewing 21 controlled trials, that bright light and dawn simulation are effective treatments for seasonal depression. But the panel said that the quality of studies was variable and that researchers should develop better standards for brightness, timing and duration.

Other approaches to seasonal affective disorder include antidepressant drugs, These have been found effective for winter depression in controlled trials. The herbal St. John’s Wort also seems to help. Patients with seasonal affective disorder may also benefit from cognitive behavioral therapy. One four-month trial found that group cognitive behavioral therapy, bright light, and a combination of the two were all equally effective.

SOURCE: HARVARD MENTAL HEALTH LETTER  Nov. 2004, Vol. 21, No. 5, pp. 4-5