What is light therapy?
Light therapy (also known as phototherapy or bright light therapy) uses light boxes emitting full-spectrum light similar in composition to sunlight. Daily exposure to this bright light is the treatment method most often recommended for patients with Seasonal Affective Disorder (SAD), a form of depression that occurs as a result of reduced exposure to sunlight in the fall, winter and spring. Light therapy may be recommended when SAD symptoms are severe enough to affect patients' daily lives. Typically, patients must sit in front of a special light box for about 30 minutes a day from the early fall until spring when outdoor light becomes strong enough to boost mood naturally. Most people with SAD respond to this treatment best when they sit in front of their boxes as soon as they wake up in the morning. Patients are instructed to sit close to the light box with their eyes open but not to look directly at the light. They can read, write or eat while seated in front of the box.
Light therapy has been reported to work in 80 percent of all cases of SAD, and some studies have found that sitting in front of a 10,000-lux (lux is a measurement of the intensity of light) light box for 30 minutes every morning is as effective for SAD patients as treatment with some types of antidepressants. Light therapy is believed to work by its effect on brain chemicals that play a role in regulating mood. This treatment can relieve symptoms within a few days, but sometimes takes as long as two weeks or more.
Another type of light therapy uses ultraviolet (UV) wavelengths for treatment of the skin disorder psoriasis and some other skin conditions, as well as for a type of cancer called cutaneous T-cell lymphoma. UV light is being studied for treatment of other skin conditions including atopic dermatitis (an allergic reaction) and vitiligo, in which skin pigmentation is uneven. The light therapy boxes used to treat SAD are designed to filter out UV light, and UV light released by tanning beds has been found to be ineffective for treating SAD.
What conditions is light therapy used for?
In addition to SAD, light therapy has been used to treat other types of depression, to boost the effects of antidepressant medication, as a substitute for antidepressants during pregnancy or while breastfeeding, and to enable patients with depression to take lower doses of antidepressants. It also has been used to treat insomnia and the eating disorder bulimia, and is being studied as a treatment for obsessive-compulsive disorders, premenstrual syndrome, jet lag, Parkinson's disease, dementia and attention deficit hyperactivity disorder (ADHD).
What kinds of health care practitioners recommend light therapy?
Light therapy for treatment of SAD may be recommended by psychiatrists and other physicians or health care professionals who treat patients with SAD or other forms of depression. While light boxes can be purchased without a prescription, a physician or other mental health professional can provide guidelines as to how to use a light therapy box for maximum effectiveness and may recommend a particular light box (you may need a doctor's prescription if you're seeking insurance coverage for the cost of a light therapy box).
Are there any side effects or conditions where light therapy should be avoided?
Individuals whose skin is especially sensitive to light, such as those with lupus (systemic lupus erythematosus) should consult a physician before attempting light therapy for any condition. You may be advised to avoid light therapy if you have a history of skin cancer or if your eyes are sensitive to light because of conditions such as glaucoma, cataracts, retinal detachment and retinopathy. In addition, light therapy has been reported to lead to mania in some patients with bipolar disorder (manic depression) and to cause suicidal thoughts. For these reasons, patients using light therapy boxes should report any mood changes or disturbing thoughts to their health care practitioners.
Certain drugs can increase sensitivity to sunlight and may cause skin reactions as a result of light therapy. These include antibiotics, anti-inflammatory drugs, some anti-histamines, lithium, the supplement melatonin and the herbal remedy St. John's wort. If you're taking any drug or supplement on a regular basis, check to make sure it won't cause a reaction to light therapy.
Some ophthalmologists have warned that blue light, part of the full spectrum of light used in light therapy, could damage the retina and increase the risk of age-related macular degeneration, a progressive eye disorder that is the leading cause of blindness in people over the age of 55. So far, however, no research has confirmed that risk.
If you're bothered by the glare from your light box, the blue light is probably responsible. You can screen it out by wearing special eyeglass lenses or clip-ons during treatment. There are also light boxes available that filter out the wavelengths believed to be most harmful.
Other side effects of light therapy are minimal. Some patients report headaches, eyestrain or eye irritation or nausea when they begin treatment, but these effects usually are mild and disappear after a few days.
Are there other therapies that might work well in conjunction with light therapy?
In some cases, patients combine light therapy with antidepressant drugs, talk therapy or cognitive behavior therapy for treatment of depression.
What is Dr. Weil's view of light therapy?
Dr. Weil has recommended exposure to bright light daily for treatment of patients whose SAD symptoms are severe enough to affect their daily lives. However, he has noted that some research suggests that cognitive behavior therapy (CBT) is very effective at preventing recurrences of SAD, perhaps even more so than light therapy, or a combination of light therapy and CBT. One advantage of CBT is that therapy may be effective after only a few weeks, while light therapy must be continued at least throughout the winter season.
Dr. Weil has also noted that the American Psychiatric Association has said that milder cases of SAD may be effectively treated with a long daily walk or by arranging your home or office so that you're exposed to a window during the day. Moving to a residence closer to the equator - where winter days are longer - can also be helpful. These may work better than therapies based on artificial light because direct sunlight is up to 130,000 lux, or about 13 times more intense than light from light boxes.
Dr. Weil views daily aerobic exercise as the most effective treatment for mild to moderate depression.
Some research suggests that a vitamin D deficiency might underlie SAD and that supplementing with vitamin D might help. Since it is estimated that more than 70 percent of the U.S. population is D-deficient, Dr. Weil recommends that everyone take a daily supplement of 2,000 IU D3 and has suggested that higher doses of D may be needed to effectively treat SAD.