1105 Effects of Daily Morning Blue Light Exposure on Subjective Sleep Quality and Mental Health

Abstract Introduction Morning exposure to blue light typically phase advances the timing of sleep onset (i.e., one falls asleep earlier) while evening light exposure delays the onset of sleep. We have previously shown that blue light in the morning increases rapid eye movement (REM) sleep compared to placebo red light. Here, we further examined the effects of morning blue light on subjective sleep, depression, posttraumatic stress, and suicidal ideation in the same sample. Methods Thirty-six participants (27 male; age=33.8, SD=6.9 years), serving in the military and meeting criteria for mild depression underwent a 6-week counterbalanced, crossover, placebo-controlled clinical trial of blue (462 nm; active) versus red (661 nm; placebo) light using a set of light exposure glasses fitted with four LEDs at the appropriate wavelength. In a cross-over design, participants were exposed to light for 30-minutes each morning for two weeks. After a 2-week washout period, participants completed a subsequent 2-week trial with the alternate light. Participants completed the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), Beck Depression Inventory-II (BDI-II), Patient Health Questionnaire-9 (PHQ-9), and PTSD Symptom Checklist (PCL-5). Results Morning blue light (relative to placebo red) was associated with a significant reduction in sleep disturbance on the PSQI and insomnia severity on the ISI (p<.05). Blue light also reduced depression on the BDI-II, and PTSD severity on the PCL-5, as well as reduced suicidal ideation on the PHQ-9 and BDI-II (p<.05). Clinical significance was calculated using the Minimally Clinically Important Difference (MCID). Blue light significantly improved (p<.05) rates of depression classification on the PHQ-9 (27% blue vs. 10.8% placebo) but not BDI-II (40.5% vs. 27%). Conclusion Daily morning blue light produced meaningful improvements in sleep quality, insomnia, depression, PTSD symptoms, and suicidal ideation compared with placebo, including clinically significant reductions in PHQ-9 depression classification. These findings suggest that brief morning blue-wavelength exposure may serve as a simple, effective adjunctive treatment for mood and sleep disturbances. Given prior evidence of increased REM resulting from morning blue light, future work should examine its role in these benefits to sleep and mental health. Support (if any) US Army Medical Research and Development Command: W81XWH2210990