An initial investigation of bright light and depression: A neuropsychological perspective

Abstract

The effects of bright and dim light on finger-tapping rate and on focused and nonfocused dichotic listening performance were evaluated in 21 nondepressed and 21 mildly depressed women. Previous research had proposed decreased left hemisphere (LH) activation in clinically depressed subjects, and pilot data projected a selective activating effect of ambient light on the LH. It was expected that those in the depressed group would have lower base rates of finger tapping, with right-hand rates affected most. The effect for groups was not significant. Bright light exposure was expected to increase the right-hand tapping rate in both groups, with a pronounced effect on depressed subjects. Group × effector × context interactions were not significant. Depressed subjects were expected to have a decreased right-ear advantage (REA) for dichotic consonant-vowel combinations; a main effect of groups was nonsignificant, but in the hypothesized direction. The depressed group also found it more difficult, but not reliably so, to focus attention on stimuli entering the right ear. Neither group experienced the predicted increase in REA in the bright light context. However, the expected increase in the depressed group’s ability to shift focus to the right ear was seen. Longer periods of light exposure, male subjects, and clinically significant populations may yield statistically significant results.