ATLANTA (CNN) — Being abused as a child may increase a mother's chance of having a child with autism, according to a new study, but researchers aren't sure why.
Investigators at The Harvard School of Public Health looked at more than 50,000 women in the Nurses' Health Study II group, and found that those who reported the highest levels of abuse as children themselves were 60% more likely to have children with some type of autism-spectrum disorder.
The reasons for the apparent connection, reported Wednesday in the journal JAMA Psychiatry, remain murky.
"We know that women who experience abuse in childhood are more likely to have (certain pregnancy-related) risk factors, like smoking during pregnancy, gestational diabetes or preeclampsia," said Andrea L. Roberts, a research associate at Harvard and lead author of the paper. "We also know that a lot of pregnancy complications and pregnancy-related risk factors have been associated with autism."
It would stand to reason, then, she says, that the increase in pregnancy complications that stem from a history of abuse would be the reason for an increase in children with autism. But that wasn't the case.
"When we put the two pieces together, we found that actually those pregnancy circumstances didn't explain the increased risk of autism in women who have been abused."
So what did?
"It's a hypothesis, and in our study, we don't have any evidence for this, but we know that women who have been abused are more likely to have signs of inflammation in their blood," says Roberts. "Women and men who have been abused also have a more exaggerated response to stress, and both of those things have been associated with autism."
Other autism experts say that while this correlation between abuse of the mother and autism in their children is intriguing, more studies need to be done to establish why this link exists.
"I think there definitely needs to be a further step," said Rebecca Schmidt, and autism researcher at UC Davis. "There need to be additional studies that really address some of the speculative parts of this study - specifically, why this link would be there."
The study's author doesn't disagree.
"The next step is trying to figure out why it is that women who have experienced abuse are significantly more likely to have a kid with autism," Roberts said. "We looked at nine pregnancy-related factors. It's possible it's something else we didn't measure, like infection."
While these findings may sound alarming, women who were abused as children shouldn't be alarmed, Roberts said.
"Among the women who experienced the most severe abuse, the rate (of having a child with autism) was only 1 in 50, so the risk is still quite low," she said.
If you're still concerned, Roberts says yoga, exercise, meditation and talking with a counselor can help reduce an increased stress response.