C-sections likely not a cause of autism, study says

Last fall some news headlines blared that a study had found that kids born via C-section were more likely to develop autism. Now, after a deeper data dive the same researchers have released an updated study suggesting that link was a coincidence.

"The overall risk of ASD [autism spectrum disorder] is very small and this most recent work suggests that most, if not all, the risk is not [due to] the cesarean section at all,” said Louise Kenny, one of the lead authors of both studies and an obstetrician and gynecologist at Cork University Maternity Hospital in Ireland.

The newest study was published Wednesday in the Journal of the American Medical Association Psychiatry. The results suggest that the slight statistical correlation in the earlier study was not proof of causation, but was rather the result of unknown genetic or environmental factors, according to the authors.

These studies add to the canon of autism research in recent years that has sought to find a cause for the disorder. The number of children with autism has grown significantly in the last decade. According to the Centers for Disease Control and Prevention, currently one in 68 children is diagnosed with autism; in 2000, the figure was one in 150.

So when the earlier study was released last fall in the online Journal for Child Psychology and Psychiatry stating that kids delivered by C-section were 23 percent more likely to develop autism, it received a lot of attention, even though the researchers were careful to note that their work had not established that the method of delivery had anything to do with the disorder.

The drama around that research inspired the follow-up study. This time around the researchers studied all births in Sweden from 1982 to 2010. In that large group, they found the same statistical outcome as the first study – a slight increase in the number of autism diagnoses for kids delivered by C-section (children born that way were 21 percent more likely to be diagnosed with autism).

Then researchers zeroed in on 13,000 pairs of siblings that included one child with the disorder. That deeper look into the sibling cohort showed no association between C-section and autism, according to the study.