The effect of zinc supplementation in children with attention deficit hyperactivity disorder: A systematic review and dose-response meta‑analysis of randomized clinical trials

Objective The present systematic review and dose-response meta-analysis was conducted to quantify the efficacy of zinc supplementation on clinical symptoms of attention-deficit/hyperactivity disorder (ADHD) in children.Methods Electronic databases including PubMed, Scopus, ISI web of science, and Google Scholar were searched until January 2021. Results were reported as standardized mean difference (SMD) with a 95% confidence interval (CI) using Hedges's adjusted g method.Results six randomized clinical trials with 489 school-aged children were identified for the meta-analysis. Our findings showed a significant effect of zinc supplementation on ADHD total scores (SMD: −0.62 Hedges' g; 95% CI: −1.24 to −0.002, p = 0.04) but not in hyperactivity scores (SMD: −0.93 Hedges' g; 95% CI: −3.31 to 1.45, p = 0.44) and inattention scores (SMD: 0.21 Hedges' g; 95% CI: −0.09 to 0.51, p = 0.17) compared to the control group. Besides, the dose-response analysis did not find any significant non-linear association between zinc supplementation dosage or duration on ADHD total scores. The certainty of the evidence was rated moderate to very low for all outcomes.Conclusion Zinc supplementation may have beneficial effects in improving ADHD symptoms in children with ADHD. Future well‐designed, large‐scale randomized controlled trials are needed to establish the benefit of zinc supplementation for ADHD.