BACKGROUND: Depression is associated with accelerated brain aging. Bright light therapy (BLT) shows promise in treating depression and alleviating cognitive deficits, but it remains unclear if BLT can improve brain age and if clinical benefits are related to changes in brain age. This study evaluates the impact of BLT on brain age in depression and explores the relationship between symptomatic improvement and changes in brain age.
METHODS: This study reanalyzed data from a double-blind, randomized controlled trial comparing BLT to dim red light (dRL) therapy. Scores from the Hamilton Depression Rating Scale-24 (HAMD-24) and the nine-item Patient Health Questionnaire (PHQ-9) were recorded at baseline and 4 weeks after therapy. Brain MRI scans estimated individual brain age gap (BAG), which was the difference between predicted brain age and chronological age. BAGs were calculated for global and cognition-specific domains (executive function, memory, language, and vision). Changes in clinical scores and BAG were assessed within and between groups, including analyses based on symptom improvement.
RESULTS: The study included 21 participants in the BLT group and 18 in the dRL group. Both groups showed improvements in clinical scores without significant between-group differences. Although there were no group differences in BAG, the combined group had a significantly younger BAG in global, vision, and language domains after intervention. Additionally, patients with improvement in PHQ-9 scores showed reduced BAG in global brain and executive function domains and greater improvement in PHQ-9 was correlated with a younger executive function brain age.
CONCLUSION: No specific effect of BLT on brain age was observed compared with the control group. However, reductions in global and executive function brain age were associated with subjective symptom improvement, suggesting a potential role of placebo effects or neuroplasticity. These findings highlight the importance of considering subjective measures and brain aging biomarkers in evaluating antidepressant interventions.
