Abstract: ObjectiveTo investigate the relationship between methylenetetrahydrofolate reductase (MTHFR) gene
polymorphism and susceptibility to autism spectrum disorders (ASD). MethodsThe relevant studies on MTHFR gene
C677T polymorphism and susceptibility to ASD databases until June 30, 2020 were searched in databases of CNKI, Wanfang
data, PubMed, Embase, Proquest and Web. Meta-analysis was conducted by using STATA 14.0. ResultsA total of 16
articles were included, including 2 149 cases in the case group and 2 251 cases in the control group. Meta-analysis showed
that MTHFR C677T polymorphism was significantly associated with an increased risk of autism in the allelic model (T vs. C,
OR=1.51, 95%CI: 1.15-1.99，P=0.003) and dominant genetic model (TT+CT vs. CC, OR=1.67, 95%CI: 1.21-2.29, P=
0.002). Analysis of ethnic subgroups showed that the MTHFR C677T polymorphism of Caucasians was closely related to the
occurrence of autism only in the dominant genetic genotype (OR=1.30, 95%CI: 1.04-1.63，P=0.024), while the Asians were
related in both the allelic model (OR=1.85, 95%CI: 1.13-3.01, P=0.014) and the dominant genetic model (OR=1.99，95%CI:

Key words: autism spectrum disorder, methylenetetrahydrofolate reductase (NADPH2), polymorphism, single nucleotide,  Meta analysis