BackgroundLight therapy is a known treatment for patients with seasonal affective disorder. However, the efficacy of light therapy in treating patients with non-seasonal depression remains inconclusive.AimsTo provide the current state of evidence for efficacy of light therapy in non-seasonal depressive disorders.MethodSystematic review of randomised controlled trials (RCTs) was conducted by searching MEDLINE, EMBASE, PsycINFO, CINAHL, and CENTRAL from their inception to September 2015. Study selection, data abstraction and risk of bias assessment were independently conducted in duplicate. Meta-analyses were performed to provide a summary statistic for the included RCTs. The reporting of this systematic review follows the PRISMA guidelines.ResultsA meta-analysis including 881 participants from 20 RCTs demonstrated a beneficial effect of light therapy in non-seasonal depression (standardised mean difference in depression score −0.41 (95% CI −0.64 to −0.18)). This estimate was associated with significant heterogeneity (I²=60%, P=0.0003) that was not sufficiently explained by subgroup analyses. There was also high risk of bias in the included trials limiting the study interpretation.ConclusionsThe overall quality of evidence is poor due to high risk of bias and inconsistency. However, considering that light therapy has minimal side-effects and our meta-analysis demonstrated that a significant proportion of patients achieved a clinically significant response, light therapy may be effective for patients with non-seasonal depression and can be a helpful additional therapeutic intervention for depression.