No antidepressant-like acute effects of bright light on emotional information processing in healthy volunteers

Abstract

Rationale Bright light treatment (BLT) is an efficacious antidepressant intervention, but its mechanism of action is not well understood. Antidepressant drugs acutely affect how emotional information is processed, pushing the brain to prioritise positive relative to negative input. Whether BLT could have a similar effect is not known to date. Objective To test whether BLT acutely influences emotional information processing similar to antidepressant drugs, using an established healthy volunteer assay. Methods Following a double-blind, parallel-group design, 49 healthy volunteers (18–65 years, 26 females) were randomly allocated to 60-min BLT (≥ 10,000 lux) or sham-placebo treatment early in the morning in autumn/winter. Immediately after treatment, emotional information processing was assessed using the Oxford Emotional Test Battery, a validated set of behavioural tasks tapping into emotional information processing in different cognitive domains. Participants also completed questionnaires before and after treatment to assess changes in subjective state. Results The BLT group did not show significantly more positively biased emotional information processing compared to the placebo group (p > 0.05 for all measures). After adjustment for pre-treatment scores, there were also no significant post-treatment differences between groups in subjective state (p > 0.05 for all measures). Conclusions BLT did not show immediate effects on emotional information processing in an established healthy volunteer assay. Thus, BLT might exert its clinical effects through a different (cognitive) mechanism than other antidepressant interventions. Future studies should corroborate this finding including clinical populations and more intensive treatment regimes, and control for potential chronobiological effects.

Increased functional connectivity between the midbrain and frontal cortex following bright light therapy in subthreshold depression: A randomized clinical trial.

“…In a previous randomized placebo-controlled trial, we verified the efficacy of BLT for symptoms of depression and anxiety in college students with nonseasonal subthreshold depression (Jiang et al, 2020). Various mechanisms for the action of light therapy have been proposed, including effects on the melatonin secretion, biological clock (circadian rhythm system), central monoaminergic signaling, interactions with serotonin, and vegetative nervous system activity (Kaltenboeck et al, 2022; Maruani & Geoffroy, 2019; Murray et al, 2005; Pail et al, 2011). Notably, light is perceived not only by rods and cones but also by a subset of retinal ganglion cells (RGCs) that express the photopigment melanopsin that renders them intrinsically photosensitive (ip) RGCs (Mure, 2021; Mure & Vinberg, 2019).…”