Blue light therapy is more effective than red light therapy for the treatment of seasonal affective disorder (SAD), according to a study published in the scientific journal Depression and Anxiety in 2009.
Seasonal affective disorder, or the “winter blues,” affects approximately 4-6% of the population. The Diagnostic and Statistical Manual of Mental Disorders does not currently list seasonal affective disorder as a unique mood disorder, rather it is listed as a specific type of major depressive disorder. As the name suggests, those affected by seasonal affective disorder experience changes in mood, usually the onset of depression, due to changes in season.
According to the authors of this study, despite the demonstrated effectiveness of light therapy, it has been mostly ignored as a treatment option for those with seasonal affective disorder. Antidepressants are often used to treat the symptoms of seasonal affective disorder, but due to the comparatively high amounts of side-effects of these medications, light therapy is an alternative treatment that should be considered.
To test the differences between blue light therapy and red light therapy, the researchers recruited 35 participants with seasonal affective disorder. Of these 35 participants, half received blue light therapy while the other half received red light therapy. Both groups received their light therapy once a week for three weeks.
The blue light therapy consisted of LED panels that emitted wavelengths of about 470nm and the red light therapy consisted of panels that emitted wavelengths of about 650nm. The participants sat in front of these light panels for an hour and were asked to periodically look at the light source.
To measure the level of depression in the participants, the authors of this study used the Hamilton Depression Rating Scale, a standardized test that is often used to measure depression.
According to the authors of this study, the participants receiving red-light therapy improved an average of 32% on the Hamilton Depression Rating Scale and those receiving blue-light therapy improved an average of 51%.
Strong, R.E., Marchant, B.K., Reimherr, F.W., Williams, E., Soni, P. & Mestas, R. (2009). Narrow-band blue-light treatment of seasonal affective disorder in adults and the influence of additional nonseasonal symptoms. Depression and Anxiety, Vol 26: 273-278.