An Examination of the Acute Effects of Bright Light Therapy in a Non-Clinical Sample

Abstract

The integral role of light in physiological and psychological well-being is illustrated by the application of phototherapy, or bright light therapy (BLT), in treating mood disorders such as seasonal affective disorder and non-seasonal depression. More recently, BLT has been applied in treating jet lag due to transmeridian travel, complications from shift work, and disorders of sleeping and waking. Despite the numerous potential applications of BLT, deleterious side effects have not been fully explored in a non-clinical population. Thus, I examined the acute side effects (nausea, headache, blurred vision, eye strain) of a single 30-minute exposure of bright white light (10,000 lux) therapy and a comparison dim red light (<500 lux) in non-depressed sample of young adults, with a focus on the potential moderating role of depressive symptoms. Linear regressions revealed no significant main effects for light. However, self-reported nausea and total side effect intensity significantly decreased in response to white light, but not red light, for those with greater depressive symptomatology. In addition, a repeated-measures analysis of variance revealed a significant group-by-time interaction for sad mood, which decreased at a higher rate in the white light condition compared to the red light condition. Also, a post-hoc analysis revealed a significant increase in eye strain for both conditions, with no significant difference between them. These results suggest that the high prevalence of acute adverse side effects in the extant BLT literature may not fully apply to non-clinical populations.