Fig. 1. MAO-A V_T reduction after BLT.

Three weeks of BLT resulted in a reduction in MAO-A V_T (F_{1, 208.92} = 25.96, p < 0.001), while placebo did not. Bars denote mean MAO-A V_T for BLT (green, SAD and HC pooled) and placebo (yellow, SAD and HC pooled), brackets denote standard error. Illustrated MAO-A V_T is averaged for all ROIs. Effects of BLT and placebo are pooled for HC and SAD because mixed model analyses of PET1 and PET2 data revealed a two-way interaction between measurement and therapy (F_{1, 385.58} = 19.16, p < 0.001). PET1 fall/winter before BLT/placebo, PET2 fall/winter after BLT/placebo. **p ≤ 0.001. MAO-A V_T: monoamine oxidase A distribution volume, BLT: bright light therapy, SAD: seasonal affective disorder, HC: healthy controls, 5-HT: Serotonin