Transcranial Laser Therapy, Continuous and Pulsed Light, for Major Depressive Disorder (ELATED-3)

During study visits a clinician applies transcranial light therapy to both sides of a participant's forehead for about 30 minutes. The study involves, 1 screening visit which may last up to the 3 hours, 24 transcranial light therapy treatment visits, and 1 post-treatment visit (26 total visits to the Massachusetts General Hospital). If a participant qualifies for the study, we assign the participant by chance to receive either active transcranial light therapy or sham transcranial light therapy treatment. During sham transcranial light therapy visits, the transcranial light therapy device will not produce near infrared waves (e.g., light energy that cannot penetrate the skin and cranium). Participants have an equal chance of being assigned to the active transcranial light therapy or the sham transcranial light therapy when first randomized. Neither the participant, nor the clinician, nor any research staff will know which study group the participant belongs. Participants are randomized a second time after 6-weeks in the study. If the participant were in the sham group the first 6-weeks, that participant may receive the active transcranial light therapy treatment after re-randomization. If the participant were already in the active transcranial light therapy group during the first 6-weeks the participant continues receiving the active treatment. All in all, participants have a 1 in 3 chance of receiving the active transcranial light therapy treatment at some point during the study.