Children born to mothers who took folic acid supplements in the weeks right before and after conception are less likely to develop autism, a new study from Norway has found.
The study, published Tuesday in the Journal of the American Medical Association (JAMA), followed 85,176 Norwegian children born in 2002-2008 for up to 10 years. The mothers had been recruited into the study during pregnancy, at which time they filled out several questionnaires, including one about any supplements they were taking. In those questionnaires, 61,043 of the women reported having used folic acid right before and after conception (from four weeks before to eight weeks after). The other 24,134 women said they had not used the supplement during that period.
At the end of the study, 114 of the children, or 0.13 percent, had been diagnosed with autistic disorder. The data revealed that the rate of autistic disorder was 0.21 percent (50/24,134) in the children whose mothers had not taken folic acid supplements around conception compared to 0.10 percent (64/61,043) in those who had.
“The mothers who took folic acid supplements in early pregnancy had a 40 percent reduction in the risk of having a child with autism,” said lead author Dr. Paul Suren of the Norwegian Institute of Public Health in a video that accompanied the release of the study.
The study did not find, he added, a similar reduction in the risk of a less severe form of autism known as pervasive developmental disorder-not otherwise specified (PDD-NOS). And the study’s cases of Asperger syndrome, a high-functioning form of autism, were too few (56) for the researchers to draw any statistical conclusions. (The American Psychological Association has recently decided to combine all autism subtypes into a single diagnostic category: autism spectrum disorder, or ASD.)
Only a correlation
It’s important to point out that this was an observational study. Its results show only a correlation, not a causation, between the use of folic acid early in pregnancy and a lower risk of autism.
Other factors may explain the lower risk of autism among the children whose mothers took folic acid. For example, in this study those women also tended to have more education and higher incomes — factors that may mean they received better prenatal care. They were also more likely to not smoke, not be overweight and to have planned their pregnancy.
Still, the findings are interesting. Folic acid supplementation early in pregnancy has already been found to prevent major birth defects that affect the brain and spine. Health officials strongly advise would-be moms to start taking 400 micrograms daily of folic acid at least four weeks before becoming pregnant.
“This study provides an indication that folic acid supplements might be preventive against autism,” said Suren. “We haven’t, strickly speaking, proved it with this study, and we don’t know what the mechanisms might be. But we still think that it provides an additional reason for women to take folic acid supplements, and it underlines the need to start as early as possible and preferably before the start of pregnancy.”
Suren said one important next step in this field of research would be to investigate the genes that regulate the metabolism of folic acid and other vitamins in the body to see if there are genetic variants that make certain children more vulnerable to folic acid deficiencies. More studies are also needed, he added, to determine whether folic acid supplementation is associated with a reduced risk of other brain disorders, such as epilepsy, cerebral palsy and attention deficit hyperactivity disorder (ADHD).
“The neural tube is the origin of the human brain, so the fact that folic acid is preventive tells us that it’s crucial at these very early stages of brain development,” he said. “And in recent years researchers have been starting to ask themselves, ‘Could it have other beneficial effects? Could it also be preventive against other brain disorders in children?’ ”
The study can be read in full on the JAMA website.