It has been hypothesized that autism spectrum disorder (ASD) may have a connection with folate insufficiency or excess, but the evidence is mixed and largely inconclusive.
Folate is undoubtedly crucial for fetal neurodevelopment during early pregnancy. Folic acid supplementation during pregnancy, often in the form of a multivitamin, has generally been associated with neutral to beneficial effects on ASD risk.[1][2] However, both high and low levels of maternal serum folate during pregnancy have been associated with an increased risk of ASD.[3][4]
Lending support to the theory of a connection between folate and ASD, a 2021 meta-analysis of observational studies found that children with ASD were 19 times more likely to have cerebral folate receptor autoantibodies, which could indicate a reduced capacity to transport folate into the brain.[5] Additionally, autism is associated with an increased likelihood of MTHFR polymorphism, suggesting impaired folate metabolism.[6]
While further research is needed to understand the relationship between folate and autism, it seems fair to suggest that folic acid supplementation at appropriate doses during pregnancy may have a neutral to beneficial effect on the risk of ASD.