Phototherapy, or light therapy, is the administration of doses of bright light in order to normalize the body's internal clock and/or relieve depression.Phototherapy is prescribed primarily to treat seasonal affective disorder (SAD), a mood disorder characterized by depression in the winter months, and isoccasionally 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 todepressive 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 thelight 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 ultravioletrays 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 boxmay 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 once. The time of day and number of times treatment is administered depend on the physical needs and lifestyle of the individual patient. If phototherapy has been prescribed for the treatment of SAD, it typically begins in the fall months as the days begin to shorten, and continues throughout the winter and possibly the early spring.
The light from a slanted light box is designed to focus on the table it sitsupon, 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).
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 thestatus 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 canalleviate 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 within2-14 days after beginning phototherapy.