Fifteen trials were identified (n=570).
Light therapy in seasonal depressed patients versus non-seasonal depressed patients.
All three studies reported statistically significantly better outcomes in patients with seasonal depression. Across the studies the percentage of non-seasonal responders varied from 0 to 14 per cent. All studies had methodological limitations.
Comparisons of bright light therapy versus placebo low intensity light condition or sham air ionisation device in patients with non-seasonal depression said to be free of antidepressants studies yielded inconsistent results: three studies found bright light to be more effective in reducing symptoms of depression than the placebo dim light condition; four other studies did not. Clinical heterogeneity was noted and the impact of a range of patient, treatment and study factors was investigated. None of the factors were found to consistently predict positive or negative outcomes.
Light therapy versus placebo low-intensity light condition in patients using antidepressant medication
Four of five studies reported positive results. No specific factors were identified to explain the results of the negative trial.