evidence: To conclude, this meta-analysis confirms that C677T polymorphism of MTHFR is remarkably linked with ASD risk. Nevertheless, the findings agree that the A1298C polymorphism of MTHFR is not significantly correlated with ASD. Exploring gene-gene and gene-environment interactions could throw more light on the genetic link between MTHFR variants and ASD risk. [...] Pu D, Shen Y, Wu J. Association between MTHFR gene polymorphisms and the risk of autism spectrum disorders: a meta-analysis. Autism Res. 2013;6:384–92. Rai V. Association of methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism with autism: evidence of genetic susceptibility. Metab Brain Dis. 2016;31(4):727–735. https://doi.org/10.1007/s11011-016-9815-0.