Can a lamp brighten your mood? Original paper

Seasonal affective disorder (SAD) usually starts in the fall/winter and remits in the spring/summer. This may be due to the change in daylight, with the darkening months leading to darkening mood and disrupted circadian rhythm. For this reason, SAD has been treated with bright light therapy (BLT), but how effective is BLT really?

This systematic review and meta-analysis of 19 randomized controlled trials explored the efficacy of BLT (1,000 lux) compared to control — which was either a dim light (<500 lux) or a sham treatment with a negative-ion generator — in adults diagnosed with SAD. The primary outcome was the post-treatment depression scores, and the secondary outcome was the rate of response to the treatment.

In 18 trials (610 participants), BLT improved depression scores, compared to control. In 16 trials (559 participants), the rate of response to BLT was greater, compared to control.

The risk of bias was high in 11 trials. However, after eliminating those trials, a sensitivity analysis for the primary and secondary outcomes showed that improvements in depression and response rates were actually greater than when all the studies were included in the calculations.

Since the 18 trials investigated only the short-term effects of BLT, no conclusions regarding BLT’s long-term efficacy can be made.