Phototherapy is prescribed primarily to treat seasonal affective disorder (SAD), a mood disorder characterized by depression in the winter months, and is occasionally employed to treat insomnia and jet lag. The exact mechanisms by which the treatment works are not known, but the bright light employed in phototherapy may act to readjust the body's circadian (daily) rhythms, or internal clock. Other popular theories are that light triggers the production of serotonin, a neurotransmitter believed to be related to depressive disorders, or that it influences the body's production of melatonin, a hormone derived from serotonin that may be related to circadian rhythms.
Patients with eye problems should see an ophthalmologist regularly, both before and during phototherapy. Because some ultraviolet rays are emitted by the light boxes used in phototherapy, patients taking photosensitizing medications (medications making the skin more sensitive to light) and those who have sun-sensitive skin should consult with their physician before beginning treatment. Patients with medical conditions that make them sensitive to ultraviolet rays should also be seen by a physician before starting phototherapy. Patients who have a history of mood swings or mania should be monitored closely, since phototherapy may cause excessive mood elevation in some individuals.
Phototherapy is generally administered at home. The most commonly used phototherapy equipment is a portable lighting device known as a light box. The box may be mounted upright to a wall, or slanted downwards towards a table. The patient sits in front of the box for a prescribed period of time (anywhere from 15 minutes to several hours). Some patients with SAD undergo phototherapy sessions two or three times a day, others only
The light from a slanted light box is designed to focus on the table it sits upon, so patients may look down to read or do other sedentary activities during therapy. Patients using an upright light box must face the light source (although they need not look directly into the light). The light sources in these light boxes typically range from 2,500–10,000 lux. (In contrast, average indoor lighting is 300–500 lux; a sunny summer day is about 100,000 lux).
Phototherapy prescribed for the treatment of SAD may be covered by insurance. Individuals requiring phototherapy should check with their insurance company to see if the cost of renting or purchasing a light box is covered.
Patients beginning light therapy for SAD may need to adjust the length, frequency, and timing of their phototherapy sessions to achieve the maximum benefit. These patients should keep their doctor informed of their progress and the status of their depressive symptoms. Occasionally, antidepressants and/or psychotherapy may be recommended as an adjunct to phototherapy.
An abnormally elevated or expansive mood (hypomania) may occur, but it is usually temporary. Some patients undergoing phototherapy treatment report side effects of eyestrain, headaches, insomnia, fatigue, sunburn, and dry eyes or nose. Most of these effects can be managed by adjusting the timing and duration of the phototherapy sessions. A strong sun block and eye and nose drops can alleviate the other problems. Long-term studies have shown no negative effects to the eye function of individuals undergoing phototherapy treatments.
Patients with SAD typically report an alleviation of depressive symptoms within two to 14 days after beginning phototherapy.
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, DC: American Psychiatric Press, Inc., 1994.
Rosenthal, Norman E. Winter Blues: Seasonal Affective Disorder—What It Is and How to Overcome It. New York: Guilford Press, 1993.
Andersen, Janis L., and Gabrielle I. Weiner. "Seasonal Depression." Harvard Health Letter 21, no. 4 (Feb. 1996): 7-9.
Rosenthal, Norman E. "Light and Biological Rhythms in Psychiatry." Harvard Mental Health Letter 11, no. 9 (Mar.1995): 5-6.
Zal, H. Michael. "Seasonal Affective Disorder: How to Lighten the Burden of 'Winter Depression'." Consultant 37, no. 3 (Mar. 1997): 641-6.
National Institute of Mental Health. Mental Health Public Inquiries, 5600 Fishers Lane, Room 15C-05, Rockville, MD 20857. (888) 826-9438. <http://www.nimh.nih.gov>.
Society for Light Treatment and Biological Rhythms. P.O. Box 591687, 174 Cook St., San Francisco, CA 94159-1687. <http://www.websciences.org/sltbr>.
Paula Anne Ford-Martin
Circadian rhythm—The rhythmic repetition of certain phenomena in living organisms at about the same time each day.
Lux—A standard unit of measure for illumination.
Neurotransmitter—A chemical in the brain that transmits messages between neurons, or nerve cells.
Photosensitivity—An abnormally heightened reaction to light.