Bright light therapy for nonseasonal depression: Meta-analysis of clinical trials

- Bright light therapy seems efficacious in improving nonseasonal depression.
- It is particularly efficacious as monotherapy and for 2-5 weeks׳ duration of exposure.
- The exposure intensity; treatment duration and study design need to be standardized.
- The efficacy of light therapy in perinatal depression needs to be further explored.

BackgroundBright light therapy (BLT) is a well-established treatment for seasonal depression. In the last two decades, the interest in BLT has expanded to involve other nonseasonal types of depression. The role of BLT for nonseasonal depression remains unsettled. In view of the growing number of studies in this area, this review aimed to assess the efficacy of BLT in nonseasonal depression.MethodsWe searched Pubmed; Scopus; PsychINFO; Evidence Based Medicine Guidelines and Cochrane Library until December 2015. The Standardized mean difference was calculated to assess the efficacy of BLT in nonseasonal depression. Data were subgrouped according to different study characteristics. Heterogeneity was assessed by examining the I2 index.ResultsNine trials met the inclusion criteria. After employing the more conservative random-effects model, the overall model showed a significant reduction of depressive symptoms after BLT administration (SMD=−0.62, P<0.001, I2=37%). In particular, BLT appears to be efficacious when administered for 2-5 weeks (SMD=−0.78, P<0.001, I2=0%), and as monotherapy (SMD=−0.71, P<0.001, I2=18%). Studies of BLT for perinatal depression have found statistically insignificant improvement (SMD=−0.17, P>0.05, I2=44%).LimitationsThe overall heterogeneity of the included trials was moderate. The participants were not adequately blinded to the intervention. The sample size was small for certain subgroups. The long-term effect of BLT on depression was not explored.ConclusionsBLT appears to be efficacious, particularly when administered for 2-5 weeks' duration and as monotherapy. There is an obvious need to optimize the duration and intensity of exposure, the timing and the duration of treatment sessions.