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When used correctly, light therapy can help alleviate the fatigue and decreased activity commonly experienced in the shorter days of fall and winter, or even into spring. It is a common treatment for SAD. (seasonal affective disorder or "winter blues").
Seasonal Affective Disorder: What Is It?
Seasonal Affective Disorder or SAD (sometimes called winter depression) is a condition characterized by recurrent depression in the fall and winter months, which alternates with nondepressed times in the spring and summer. In fall and winter, people with SAD usually experience an increase in vegetative symptoms including oversleeping, overeating, carbohydrate craving weight gain, fatigue, and social withdrawal. Many people with SAD note a marked responsiveness to changes in climate, latitude, and light conditions. Mood may lighten and energy may increase when a person with SAD spends more time in areas with windows or when the weather improves. Mood and energy may deteriorate when the amount of environmental light is reduced.
How Can Light Therapy Help?
Regular exposure to light of sufficient intensity, even artificial light, has been shown to ameliorate the symptoms of SAD for some people. Regardless of the mechanism, the findings that light therapy is a viable treatment for winter depression are widely supported.
People who are responsive to light therapy will generally see some effect after a week of treatment, although two weeks of treatment or more produces the greatest effects. Morning exposure has been shown to be somewhat better at achieving relief of symptoms than evening exposure. The symptoms most likely to respond to light treatment include: hypersomnia (oversleeping), carbohydrate cravings, afternoon and evening "slumps," and reverse diurnal variation, where evenings are worse than mornings. Symptoms less likely to be responsive include melancholic symptoms, suicidality, appetite loss, feelings of guilt, insomnia, and typical diurnal pattern, where mornings are worse than evenings.
What Are Possible Side Effects?
Although negative side effects are uncommon, people sometimes complain that light therapy causes irritability, eyestrain, headaches, sleep disturbances or insomnia. The latter is most likely to occur when people use the light source in the evening. Mild visual side effects are common but remit promptly. Side effects can generally be reversed by decreasing the duration of treatment or increasing the distance between the patient and the light source.