Li Y, Qiu S, Shi J, et al. - Given that autism spectrum disorder (ASD) is one of the complex neurodevelopmental disorders, which has been increasingly recognized as a public health issue, researchers conducted this investigation to explore associations between MTHFR polymorphism (C677T/A1298C) and susceptibility to ASD. A total of 15 manuscripts published up to January 26, 2020, were chosen from PubMed, Google Scholar, Medline, WangFang, and CNKI databases using search terms “MTHFR” OR “methylenetetrahydrofolate reductase” AND “ASD” OR “Autism Spectrum Disorders” OR “Autism” AND “polymorphism” OR “susceptibility” OR “C677T” OR “A1298C”. According to this meta-analysis, MTHFR C677T polymorphism is a susceptibility factor for ASD, and MTHFR A1298C polymorphism is not related to ASD susceptibility.