PMC

Average hourly light exposure for the 7-day period prior to the baseline measurements (black line), and during the 7-day period of morning light therapy (red line). Asterisks indicate periods of time where the average hourly light exposure was significantly greater (p < 0.05) during the week of morning light therapy. Error bars represent ± the standard error of the mean hourly light exposure. The extra light exposure due to the light therapy was accounted for in this analysis by adding an additional 500 lux of light exposure to the recorded ambient light exposure for each minute of the diary-reported 30-minute period that each participant wore the light therapy glasses on each day of the light therapy week (the mean reported time that the light therapy glasses were worn was 07:08 am ± 00:51 min; range: 05:30 to 11:01am).

Flowchart of overview study. DSM = Diagnostic and Statistical Manual of Mental Disorders; BLT = bright light therapy; DRLT = dim red light therapy

Serotonin transporter binding potential (5-HTT BP_ND) measured across conditions in six brain regions of interest (ROIs) during the winter (n = 10). Open (placebo) and closed (light therapy) triangles represent individual subject 5-HTT BP_ND values for each condition, and red bars represent the group mean. ACC refers to anterior cingulate cortex. 5-HTT BP_ND was significantly decreased in the ACC of healthy individuals following light therapy relative to placebo. Trend-level reductions in 5-HTT BP_ND were also observed in the ventral striatum and hippocampus. Error bars were omitted for clarity.

Heating of microvessels containing red blood cells and artificial red cells by light therapy equipment.