Oxidative stress-related biomarkers in autism: Systematic review and meta-analyses

► We reviewed studies on biomarkers related to oxidative stress in autism. ► Glutathione (GSH), transmethylation, and transsulfuration pathways were altered. ► Blood GSH, glutathione peroxidase, methionine, and cysteine decreased, whereas blood oxidized glutathione increased. ► No association with blood vitamin levels was found. ► Carriers of the mutant C677T allele in the MTHFR gene had higher risk of autism.