Many people suffer from a type of depression known as seasonal affective disorder (SAD). The disorder occurs most often during the winter months when natural sunlight levels are reduced. Some scientists believe that supplementing SAD sufferers with bright light from light therapy boxes can help the afflicted overcome their feelings of depression or winter blues.
Symptoms of SAD typically begin to appear in the autumn as days grow shorter and temperatures get colder. The disorder is more common in northern latitudes that have fewer yearly hours of sunlight. Symptoms include fatigue, loss of appetite, weight loss, irritability, insomnia, and crying spells. SAD is found in people of all ages, is more common in women than men, and often recurs annually.
One therapy thought to be effective in treating SAD is light therapy, also known as bright light therapy or phototherapy. With phototherapy, a person sits near a type of lamp called a light therapy box. It emits bright full-spectrum light that is much like natural sunlight.
Light intensity, both natural and artificial, is measured in lux. A typical home environment has a light intensity of 100 to 300 lux. Light therapy boxes emit light that hits a person's retina at an intensity of 2,000 to 10,000 lux. Most light therapy practitioners recommend a light intensity of 10,000 lux.
Researchers believe a person's biological clock is important in his or her feelings of well-being. They think a certain amount of daylight is necessary for a person to be in sync with his or her biological clock. Phototherapy is thought to adjust the biological clock of light-deprived individuals.
Light therapy boxes can also alter circadian rhythms and inhibit the release of melatonin — a natural sleep aid. Light therapy may increase the body's release of serotonin, which is a natural mood enhancer. To induce these changes, therapists recommend that people expose themselves to the bright light for 15 to 30 minutes a day when suffering from the signs of depression. Patients undergoing light box therapy will usually begin to feel relief within a week of starting the therapy.
There are few known side effects from using light therapy boxes. Developers removed the ultraviolet radiation from the spectrum of the emitted light, so no harmful radiation reaches a patient's eyes. Light therapy is used most often to treat milder forms of depression, but researchers are looking at using light therapy to treat more serious forms of mental illness. It may also be helpful in treating sleep disorders, problems adjusting to an irregular work schedule, and jet lag.
