Light Therapy

Section: Seasonal Affective Disorder
Many of us are aware of sunshine's elevating effect on the spirit, particularly after a stretch of gray days. For people who suffer from seasonal affective disorder -- a clinical depression that persists throughout the dark months -- light is more than a pleasant break in the weather; it's a medical prescription. Exposure to bright light, or phototherapy, is now the "first-line" treatment for alleviating symptoms of this major depressive disorder, and can be implemented both indoors and out.

People who have seasonal affective disorder (SAD) often feel depressed, lack energy, and sleep too much or too little. An increased appetite, usually with carbohydrate cravings, is common. So is weight gain.

SAD afflicts an estimated 6% of American adults. It becomes more prevalent the farther one goes from the equator. Women experience SAD three to four times more frequently than do men, and it is most common among people ages 20-50. A milder form of seasonal depression, called winter blues, affects an additional 14%. Overall, about one in five adults is adversely influenced by winter's short periods of daylight.

The rationale for phototherapy is rooted in increasing evidence of light's influence on the body. Light consists, in part, of energized particles called photons, which act on the retina to transmit signals to the brain. Light is thought to stimulate blood flow to the brain and regulate concentrations of neurotransmitters, chemicals that deliver messages within the brain. It thus plays a role in setting our internal clock and establishing our mood.

As morning light shines into our eyes, it informs the brain that a new day has dawned. Taking this cue, the body suppresses production of the hormone melatonin, which helps regulate the sleep cycle. Light also promotes an increase in the level of the neurotransmitter serotonin, which imparts feelings of satisfaction and satiety.

The first report describing light therapy as an effective treatment for SAD was published in 1984. Today, it is considered the primary treatment for the condition.

As light therapy has evolved, it has become evident that both the quality and quantity of light are important. White light (light composed of varying wavelengths across the entire visible spectrum) is considered sufficient; ultraviolet light is no longer deemed necessary. Researchers have also found that it takes more than a little lux (a term used to quantify brightness) to produce therapeutic effects. The 10,000 lux generally recommended to treat SAD is considerably more than the 500 lux that is standard illumination in homes and offices. Less-intense light -- 2,500-5,000 lux -- can also be used over a longer period for the same degree of exposure. However, there is some evidence that the higher dose produces a more immediate, and perhaps longer-lasting, response than less intense light does.

Light boxes, which employ fluorescent bulbs housed behind a protective filter, are the most common devices for light therapy. They differ in size and portability and may have more than one setting. They work best when the user sits at a proper distance and height from the box, keeping eyes open and looking ahead or slightly downward, as illustrated. (Looking directly at the box is neither necessary nor advisable.)

Battery-operated light visors deliver bright light with less intensity but more convenience, allowing the user to move about during a session. However, whether the user is trading effectiveness for convenience remains to be seen: The results of studies testing the visors against light boxes have yielded mixed results.

Dawn simulators, which regulate light so that it gradually increases in intensity over 1.5-2 hours, offer another potential mode of therapy. Early data indicate that these devices may be effective, particularly in early winter.

The regimen of light therapy depends upon the severity of a person's symptoms. In the changing daylight of autumn, 15 minutes of 10,000-lux light once a day, right after waking up, may suffice. (Research indicates that morning sessions are more effective than evening ones.) Light exposure may then be gradually increased to 30 or 45 minutes per session. However, severe SAD may warrant even longer exposure. For example, when one's mood, energy level, and personal relationships are suffering, therapy may start with 45-minute sessions both morning and evening.

Just as individual light regimens may differ substantially, so may a person's response. Between 53% and 67% of people with SAD benefit from light therapy. Those with milder depression, or winter blues, have a slightly higher response rate: 60-80%.

Most people begin to feel the benefits of phototherapy after 2-4 days, although some may begin to perk up within 24 hours. In addition, the effect may gradually increase during the next several weeks.

Although the effects of long-term phototherapy have not yet been established, it appears to be safe to use for short periods. Yet some precautions do apply. Phototherapy may exacerbate certain eye conditions, and an eye exam may be in order. Anyone with a retinal disorder, such as macular degeneration or a diabetes-related condition, is a poor candidate for phototherapy.

People with mild seasonal depression may elect to try light therapy on their own, but those with full-fledged SAD should see a clinician first before starting the treatment. For someone who is seriously depressed, light therapy should be carefully designed and monitored; using it improperly may cause disconcerting side effects, such as rapid, intense mood swings.

The side effects of phototherapy include headache, nausea, fatigue, irritability, dizziness, eyestrain, insomnia, and excitability or a feeling of being "wired." However, they are usually mild and short-lived, and rarely severe enough to cause patients to abandon treatment. Several studies suggest that light visors may produce more side effects than light boxes.

Light boxes are rather expensive, priced between $200 and $500 per unit. Some insurers reimburse the cost, and patients may be able to rent one for a trial period.

If light therapy hasn't diminished SAD symptoms within 2 weeks -- or if the person feels even worse -- additional measures can be tried. Those that have been successful include aerobic exercise (especially in sunlight or near a light box), stress management techniques, psychotherapy, and antidepressants, such as selective serotonin reuptake inhibitors (SSRIs) like fluoxetine (Prozac). In one small preliminary study, Hypericum perforatum (St. John's wort), an herbal remedy used to treat depression, reduced symptoms of SAD when used in conjunction with light therapy.

If you're not suffering from SAD but are feeling the winter blues, a few relatively simple measures might help. Set your alarm clock to go off at sunrise, to take advantage of as much natural daylight as possible. Go for a brisk walk during your lunch hour. Take up outdoor activities. Don't be deterred by the snow; it provides a reflective surface that intensifies the light.

Scientists continue to learn more about the benefits of light therapy as they investigate its use for conditions other than SAD. Studies indicate that it can help control the eating disorder bulimia nervosa and may reduce symptoms of premenstrual syndrome (PMS). Phototherapy has also been effective in resetting circadian rhythms, including abnormal sleep-wake cycles due to shift work or jet lag. For individuals who snooze at times outside the normal sleep schedules, light therapy -- and light avoidance -- at certain times of the day can reset the sleep/wake clock. For example, it may help "night owls," who usually stay up long after midnight, and "larks," who habitually wake long before dawn, to get in sync with the rest of the world.

Treating SAD is giving us only a glimpse of phototherapy's potential. The use of bright-light treatments will no doubt continue to expand in the years ahead.

Rosethal, Norman E. Winter Blues: Seasonal Affective Disorder. 3rd edition, Guilford Press, 1998

Soceity for Light Treatment and Biological Rhythms, 10200 W.44th Avenue, Suite 304, Wheat Ridge, CO 80033-2840, web site

National Institute of Mental Health 1-800-421-4211

National Mental Health Association, 1021 Prince Street, Alexandria, VA 22314-2971, 1-800-969-6642.

National Organization for Seasonal Affective Disorder, P.O. Box 40133, Washington, DC 20016

For more technical discussion, see:

Lam, Raymond W. (editor). Seasonal Affective Disorder and Beyond: Light Treatment for SAD and Non-SAD Conditions. American Psychiatric Association, 1998.

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