Major Depressive Disorder (MDD) is a chronic disease characterized by a high prevalence, low cure rate, and significant disability. Globally, depression is recognized as the leading cause of illness and disability among children and adolescents. Bright light therapy (BLT) has been established as an effective treatment for seasonal affective disorder and has demonstrated considerable efficacy in adult patients with MDD. However, its application in adolescent patients with MDD remains largely unexplored. The aim of this clinical trial is to evaluate the clinical efficacy, onset time, safety, and applicability of BLT in adolescents with MDD and to explore the potential neural mechanisms by which BLT enhances emotional and cognitive function in this population. This is a multicenter, randomized, controlled, double-blind study. It will involve adolescents aged 13 to 17 who are either untreated or have been stable on medication for at least one week. Adolescents with MDD will be randomly assigned to one of three groups: a high-intensity bright white light intervention group, a medium-intensity bright white light intervention group, and a placebo control group receiving dim red light. Each group will undergo four weeks of light exposure, six days per week, for 40 minutes daily between 6:30 and 10:00 AM. During the light exposure period, follow-up assessments will be conducted every weekend, and participants will be followed for two weeks after the completion of light exposure.The primary outcome will be the change in total scores on the 17-item Hamilton Rating Scale for Depression (HAMD-17) from baseline to week 4. Secondary outcomes will include response and remission rates, time to onset, maintenance of efficacy, self-reported depressive symptoms, sleep quality, cognitive function, anxiety, irritability, suicidal ideation, non-suicidal self-injury, self-efficacy, and the overall safety profile of BLT.
Additionally, the study will include healthy adolescent controls and collect functional Near-Infrared Spectroscopy (fNIRS) from both the adolescent participants with major depressive disorder and the healthy controls at baseline. The fNIRS and MRI data will also be collected from the adolescent participants with MDD at the end of the intervention, in order to investigate the potential neural mechanisms by which light therapy alleviates depressive symptoms in adolescents.