Zinc as an adjunct to antidepressant medication: a meta-analysis with subgroup analysis for different levels of treatment response to antidepressants.

RESULTS: We performed random effects meta-analysis We computed a weighted effect size (Hedges' g) for the difference of the absolute scores of the Hamilton Depression Rating Scale between the group given zinc and the group given placebo after 6 and after 12 weeks. We performed subgroup analysis according to whether not it was stated in the original studies that patients in a clinical trial or subgroup within a trial had not reached remission with previous treatment with a standard antidepressant during the same illness episode. After 6 weeks, we obtained the following effect sizes: Overall effect size: Hedges' g = -0.67, p = 0.03. Subgroup with documented non-remission: Hedges' g = - 0.97, p = 0.001. Group without documented non-remission -0.35, p = 0.24. After 12 weeks: Overall effect size: Hedges' g = -1.0, p = 0.03. Subgroup with documented non-remission: Hedges' g = - 1.46, p < 0.001. Group without documented non-remission: Hedges' g = - 0.54, p = 0.07. CONCLUSIONS: We provide preliminary evidence for the efficacy of zinc vs. placebo as an adjunct to antidepressant medication.