Optimizing Light Wavelength for Treatment of Seasonal Affective Disorder

Studies report as many as 1 out of every 5 Americans is affected by mild to severe Seasonal Affective Disorder (SAD, winter depression). Although the exact cause of this condition is unknown, bright light has proven to be an effective therapeutic treatment for many people with SAD. The light sources that have been traditionally used for treatment of SAD produce white light with great variability in the balance of wavelengths that are emitted across the visible spectrum. Although several studies have attempted to test the effectiveness of different wavelengths for treatment of SAD, the devices used in those studies employed broad bandwidths of light. With the technological advancements in light emitting diodes (LEDs) the production of new light therapy equipment with much narrower bandwidths of light is possible. Side effects of exposure to traditional white light therapy for SAD have included hypomanic activation, irritability, headache, eyestrain and nausea. We hypothesize that when the wavelength of light therapy is optimized, it should be feasible to elicit strong therapeutic benefits with lower light intensities and fewer side effects. Previous studies, approved by the Jefferson IRB and successfully completed by our laboratory have shown that some colors of light are more effective in treating SAD than other colors.