Abstract
RationaleBright 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.ObjectiveTo test whether BLT acutely influences emotional information processing similar to antidepressant drugs, using an established healthy volunteer assay.MethodsFollowing 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.ResultsThe 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).ConclusionsBLT 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.
Highlights
Bright light treatment (BLT) is a non-pharmacological therapeutic modality whereby patients are exposed to highintensity white light in order to mimic increased sunlight exposure
The “cognitive neuropsychological model of antidepressant treatment action” (CONEMATA) that resulted from this line of enquiry suggests that, regardless of their idiosyncratic neurobiological targets, antidepressants exert their clinical effects via a shared ability to push emotional information processing towards a preference for positive relative to negative input (Harmer et al 2017; Roiser et al 2012; Warren et al 2015)
It has been demonstrated that blue light exposure in healthy volunteers can acutely alter brain activity in response to negative emotional vocal stimuli (Vandewalle et al 2010). These findings suggest that BLT could show acute effects on behavioural measures of emotional information processing as would be predicted by the CONEMATA
Summary
Bright light treatment (BLT) is a non-pharmacological therapeutic modality whereby patients are exposed to highintensity white light in order to mimic increased sunlight exposure. Reported effect sizes seem comparable to those of commonly used antidepressant drugs (Golden et al 2005), but BLT shows a faster onset of clinical effects and a more favourable side effect profile (Maruani and Geoffroy 2019; Oldham and Ciraulo 2014). Despite these advantages, the mechanisms through which BLT exerts its clinical effects. The “cognitive neuropsychological model of antidepressant treatment action” (CONEMATA) that resulted from this line of enquiry suggests that, regardless of their idiosyncratic neurobiological targets, antidepressants exert their clinical effects via a shared ability to push emotional information processing towards a preference for positive relative to negative input (thereby inducing a “positive bias”) (Harmer et al 2017; Roiser et al 2012; Warren et al 2015)
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