Folic acid around conception is linked to a lower autism risk
The short answer
Taking folic acid around the time of conception is consistently linked to a lower risk of autistic disorder in the child - one of the better-supported findings in this area. It's an association, not proof, and folic acid is already recommended in early pregnancy anyway.
The key studies
In 85,176 children, folic acid around conception was linked to about 39% lower odds of autistic disorder (OR 0.61, 95% CI 0.41-0.90).
Suren et al. (2013) · JAMA
A large cohort found maternal folic acid and multivitamin use before and during pregnancy linked to a lower risk of autism spectrum disorder in offspring.
Levine et al. (2018) · JAMA Psychiatry
A meta-analysis pooling multiple studies found maternal folic acid supplementation associated with reduced odds of autism spectrum disorders.
Folic acid & ASD - meta-analysis (2017)
What the research shows
In a large Norwegian study of about 85,000 children, mothers who took folic acid from roughly 4 weeks before to 8 weeks after conception had about a 40% lower risk of having a child with autistic disorder. Later cohort studies and meta-analyses have repeatedly found the same direction.
What it means for you
This adds to the long-standing reasons to take folic acid around conception and in early pregnancy - it also prevents neural-tube defects. It's about lower risk on average, not a guarantee, and it does not mean folic acid prevents autism, nor that not taking it causes it.
By the numbers
85,176 children; odds of autistic disorder about 39% lower with folic acid around conception (OR 0.61, 95% CI 0.41-0.90); 0.10% vs 0.21% of children affected (Suren 2013).
What we still don't know
Whether folic acid is directly responsible, and the biological mechanism behind the link.
The honest caveat
This is observational - it shows a consistent association, not proof that folic acid itself lowers the risk, since mothers who supplement may differ in other ways. The timing window around conception matters, and the effect was clearest for autistic disorder specifically (not other autism-spectrum subtypes).
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