Toward the Precision Medicine for a Psychiatric Disorder: Light Therapy for Major Depressive Disorder with Neuroimaging Validation

In recent therapeutic studies, light therapy has been used to treat seasonal depression disorder in countries where there is insufficient daylight during winter. Previous light therapy studies have used one treatment for all patients, irrespective of individual differences and drug control. Although light therapy has been extended to uses in a few psychiatric treatment programs for major depressive disorder (MDD), there is a lack of consistent research and conclusion regarding its effects of different combinations of lights and the neural mechanism underlying the improvement after therapy. The present study intends to propose several combinations of lights using the beneficial physical properties in prior research and validate the efficacy of the therapies with neurophysiological techniques. Twelve patients suffering from major depressive disorder were enrolled in the study. Five were in the experimental group who will receive the two-month light therapy, with 1 female and 4 males, aged from 38 to 63 years old (mean = 49, SD = 8.51). Seven were in the control group, with 5 females and 2 males, aged from 32 to 53 years old (mean = 42.71, SD = 8.56). All participants were scanned when they were enrolled in the program, a month after pure drug treatment. The control group were scanned a month after their light therapy, and the last time after the light therapy were completed. Results revealed that the default mode network and the salience network were altered after the therapy. The self-report of life quality was better after the therapy. The conclusion is that light therapy could have a lasting effect on the brain by changing the neural connectivity, which led to the improvement in patients with MDD.