Chemical Elements in Hair and Their Association with Autism Spectrum Disorder: A Comprehensive Systematic Review

Background: Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition with increasing prevalence. This review aims to systematically investigate the relationship between the levels of toxic and trace elements in hair and the occurrence of ASD. Methods: Original articles reporting trace element levels in hair were included. A comprehensive search was conducted in databases such as Medline (via PubMed), Scopus, Web of Science, and Google Scholar, covering publications from 1 January 2000, to 2 January 2023. Keywords including “hair element analysis”, “trace elements”, and “autism”, were utilized in the search. Results: A direct comparison of the data was not possible due to the variety of methodologies observed in the available studies, including variations in sample sizes and analytical procedures. Conclusions: Exposure to toxic elements, notably Mercury (Hg) and Lead (Pb), which act as neurotoxicants, was found to be associated with the pathogenesis of ASD. Furthermore, a significant correlation was identified between the Zinc (Zn) to Copper (Cu) ratio and ASD.