The Treatment of Seasonal Affective Disorder Throws Light on Dark Moods

Winter is coming, 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 02 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 b right light is often an effective treatment.

Seasonal affective disorder is defined as depression that occurs repeatedly at the same time of year, usually staring in the fall and ending in the spring.  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 often they have atypical physical symptoms, such as over-eating and excessive sleep.

Night and Day

Seasonal depression is thought to be more common and longer lasting at high latitudes, so it appears to be the result of changes in the length of the day.  But more than lost sunlight may be involved.  Many physiological rhythms – sleep and waking, body temperature, energy – are circadian, that is, have a period of 24 hours.  Internal biological clocks set these cycles, but they are also adjusted daily by synchronization with the sun.

According to a popular theory, the phase shift theory, this internal clock does not adjust to later dawns and earlier sunsets in people with seasonal affective disorder.  People with seasonal affective disorder are arising at a time when their bodies insist on sleep, with unfortunate effects on mood and energy levels.  Some patients with winter depression say they feel as though they could hibernate.

One of the cycles regulated by the brain’s pacemaker is the secretion of the hormone melatonin by the  pineal gland.  Turned on in the evening and office in the morning, melatonin secretion induces sleep and may help to synchronize other circadian rhythms.  One possibility is that people with seasonal affective disorder produce too much melatonin or are hypersensitive to the hormone.

Experiments have shown that the cycles persist even in people who are not exposed to changes in daylight because they remain indoors in windowless rooms.  And it’s been found that the activity of many individual cells, both in the brain and in the various body tissues, has a 24-hour rhythm.  These cycles are controlled by the cells own genes and respond to external signal independent of the brain.  So even if the brain’s pacemaker is reset when the day becomes shorter, other body clocks may fall behind.  And there are reciprocal effects of the sleep-wake cycle on the brain’s pacemaker as well.  The interactions have not all been worked out; the precise relationship between seasonal affective disorder and circadian rhythms remains unclear and may be different in different people.

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 mental reflector, with a plastic screen that filters out damaging ultraviolet frequencies and diffuses the light to prevent glare.  The box sits on a tabletop and the patient sits nearby for a half-hour to two hours a day.

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.

Improvement begins in a few days, and treatment continues throughout the winter.  There are few side effects, mainly occasional headaches or eye strain.  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.

Other Approaches

Antidepressant drugs, chiefly the selective serotonin reuptake inhibitors (Prozac, Zoloft, Celexa) have been found effective for winter depression in controlled trials.  The herbal St. John’s wort also seems to help.  Melatonin, although it may relieve symptoms of jet lag, has not been proved to 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.