The Relationship Between the Level of Copper, Lead, Mercury and Autism Disorders: A Meta-Analysis

BACKGROUND AND OBJECTIVES: There is a likelihood of a possible relationship between the concentrations of copper, lead, and mercury and autism. The present review was carried out to determine the relationship between the concentrations of these elements and autism by meta-analysis. METHODS: In this study, searching Scopus, PubMed, and Science Direct databases, 18 articles conducted in different countries from 1982 to 2019 were collected. Studies’ heterogeneity was investigated using the I(2) index. The data were analyzed using R and STATA software. RESULTS: In these 18 studies, 1797 patients (981 cases and 816 controls) aged 2 to 16 years were examined. Concentration of the samples (blood, hair, and nails) for both case and control groups was evaluated. There was no significant relationship between copper concentration and autism (SMD (95% CI): 0.02 (−1.16,1.20); I(2)=97.7%; P=0.972); there was a significant relationship between mercury concentration and autism (SMD (95% CI): 1.96 (0.56,3.35); I(2)=98.6%; P=0.006); there was also a significant relationship between lead concentration and autism (SMD (95% CI): 2.81 (1.64,3.98); I(2)=97.8%; P=0.000). CONCLUSION: There is, nevertheless, a significant relationship between mercury concentration and autism. Thus, the concentration of mercury can be listed as a pathogenic cause (disease-causing) for autism.