Supplementation with folic acid around the time of conception has been found to reduce the risk of neural tube defects in children, such as spina bifida, and emerging evidence also suggests that such supplementation is associated with reduced risk of other disorders related to impaired development of the nervous system, including autism spectrum disorders.
To test the association, researchers sampled data for 85 176 children born in 2002 to 2008 who were enrolled in the Norwegian Mother and Child Cohort Study and followed up through March 31, 2012. Mothers were asked about folic acid intake from 4 weeks before to 8 weeks after the start of pregnancy, defined as the first day of the last menstrual period before conception. By the end of the follow-up period, 270 of the children had been diagnosed with an autism spectrum disorder, which includes autistic disorder (114 children), Asperger syndrome (56 children), and pervasive developmental disorder–not otherwise specified (PDD-NOS) (100 children). Among children whose mothers took folic acid, 0.10% (64/61 042) had autistic disorder compared with 0.21% (50/24 134) of children whose mothers did not.
Lead author Pål Surén, MD, MPH, of the Norwegian Institute of Public Health in Oslo, discusses his team’s findings:
news@JAMA: What prompted you to look at folic acid and autism risk?
Dr Surén: There is a large ongoing study in California looking at prenatal supplements containing folic acid that has already found that women taking these supplements had a lower risk of having children with autism, but the study couldn’t distinguish clearly between folic acid or the other components in the supplements. We, too, looked at all types of dietary supplements but separated the components, and the only one associated with lower risk was folic acid. We also looked at fish oil supplements and didn’t find any associations with reduced risk.
news@JAMA: You found an association between early folic acid use and reduced risk of autism in children, but can you say your findings have proven that folic acid prevents autism?
Dr Surén: We haven’t proven folic acid is protective against autism; our trial findings show it might be. The ideal way to prove a preventive effect would be through a randomized controlled trial comparing children born to mothers taking folic acid to children born to mothers not taking folic acid. But that cannot be done, as it would be unethical to withhold folic acid, which is proven to reduce the risk of neural tube defects, from women in the control group.
news@JAMA: Although no trial can be conducted to definitively prove the benefits of folic acid in reducing autism risk, shouldn’t we be seeing a decline in autism rates in the general population as early folic acid supplementation is being adopted as part of routine care for women who are planning to conceive or those who have just become pregnant?
Dr Surén: It could decline if our findings are tied to a true biological relationship, but the decline may not be great. We found this association for only autistic disorder, the most severe form of autism. We didn’t find any association for folic acid reducing the risk of Asperger syndrome or PDD-NOS.