Light Therapy and Seasonal Affective Disorder
Seasonal Affective Disorder:
People with this condition lose steam when the days get shorter and the nights longer. Symptoms of seasonal affective disorder include loss of pleasure and energy, feelings of worthlessness, inability to concentrate, and uncontrollable urges to eat sugar and high-carbohydrate foods. Although they fade with the arrival of spring, seasonal affective disorder can leave you overweight, out of shape, and with strained relationships and employment woes.
We don’t know exactly why seasonal affective disorder occurs. According to a review published in the American Family Physician, there are probably several different causes, including changes in the body’s natural daily rhythms (circadian rhythms), in the eyes’ sensitivity to light, and in how chemical messengers like serotonin function.
Some people find that taking an antidepressant medication helps. A unique approach is the use of light therapy.
The value of light
If lack of sunlight causes or contributes to seasonal affective disorder, then getting more light may reverse it. Bright light works by stimulating cells in the retina that connect to the hypothalamus, a part of the brain that helps control circadian rhythms. Activating the hypothalamus at a certain time every day can restore a normal circadian rhythm and thus banish seasonal symptoms.
Light therapy entails sitting close to a special “light box” for 30 minutes a day, usually as soon after waking up as possible. These boxes provide 10,000 lux (“lux” is a measure of light intensity). That’s about 100 times brighter than usual indoor lighting; a bright sunny day is 50,000 lux or more. You need to have your eyes open, but don’t look at the light. Many people use the time to read a newspaper, book, or magazine, or catch up on work.
Light therapy is at least as effective as antidepressant medications for treating seasonal affective disorder.1
In efforts to make light therapy more effective, researchers are looking to improve it in various ways. One approach is creating light boxes that simulate dawn and sunrise, gradually increasing in intensity from darkness to 300 lux.
Light Therapy Vs Pharmacotherapy
Few trials have compared the effectiveness of light therapy versus pharmacotherapy. One double-blind randomized controlled trial assigned 96 patients to one of two regimens: (1) eight weeks of 10,000 lux light therapy for 30 minutes daily as soon as possible after waking plus a placebo capsule, or (2) eight weeks of 20-mg fluoxetine per day plus 100 lux light therapy (placebo) for 30 minutes daily.[2] Clinical response and remission rates for the two groups were similar, but the group receiving light therapy at the higher dosage had an earlier response and slightly lower rate of adverse effects compared with the fluoxetine group. The authors concluded that light therapy and fluoxetine are comparably effective and well tolerated, and that other clinical factors, including patient preference, should guide the selection of treatment.
Michael Craig Miller, M.D. Senior Editor, Mental Health Publishing, Harvard Health Publishing
Lam RW, Levitt AJ, Levitan RD, et al. The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder. Am J Psychiatry. 2006;163(5):805–812.