Background: The efficacy of bright light therapy is well established for winter depression but its status in depression without seasonal pattern is unclear.
Methods: We systematically evaluated available data on the efficacy of light therapy in nonseasonal depression.
Results: We identified 62 reports among which 15 met our predefined selection criteria. The available data show evidence for the efficacy of light therapy as an adjuvant treatment to antidepressants. Trials that evaluated light therapy alone (without antidepressants) in nonseasonal depression yielded inconsistent results.
Limitations: Most of the studies extracted poorly controlled the issue of blindness and were limited by small sample sizes. Publication bias may have distorted our estimation of the effect of light therapy.
Conclusions: Overall, bright light therapy is an excellent candidate for inclusion into the therapeutic inventory available for the treatment of nonseasonal depression today, as adjuvant therapy to antidepressant medication. Future clinical trials of light therapy should distinguish homogenous subgroups of depressed patients in order to evaluate whether light therapy may eventually be considered as stand-alone treatment for specific subgroups of patients with nonseasonal depression.