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.
Keywords: Zinc; attention deficit hyperactivity disorder; clinical trials; meta-analysis.