Women who were abused during childhood may face a higher risk of having a child with an autism spectrum disorder, according to new findings.
Women in the study who experienced the highest levels of physical and emotional abuse were 60 percent more likely to have a child with autism than women who weren't abused, the study found.
The most severe combination of physical, emotional and sexual abuse meant a woman in the study was 3.5 times more likely to have an autistic child than a woman who hadn't been abused, said lead study author Andrea L. Roberts, research associate in the department of social and behavioral sciences at the Harvard School of Public Health.
The researchers examined questionnaire data from more than 52,000 women enrolled in the Nurses' Health Study II, a large study of women's health that began in 1989.
Of the women in the study, 451 had a child with autism.
To assess whether the women had been abused during childhood, the researchers asked if the surveyed women had ever been hit hard enough to be bruised, or been struck by a belt or other object, and if they had been subjected to cruel punishments, insulting comments or screaming. Researchers also asked the women if they had ever experienced unwanted sexual touching or forced sexual contact by an adult or older child.
The researchers also investigated whether pregnancy-related risk factors, which have been associated with autism, further raised the risk for the condition. These risk factors include gestational diabetes, preeclampsia and premature birth. Other risks, such as smoking, use of medicines called selective serotonin uptake inhibitors and abuse by an intimate partner during pregnancy, were also examined.
Results showed that while the abused women more frequently suffered pregnancy-related risk factors, these factors explained only a small part of the link found between child abuse and autism risk.
The study shows an association, not a cause-and-effect link, researchers said, and it's not clear how childhood abuse may contribute to autism.
But there are plausable ways to explain the association. One idea is that abused women may have a heightened response to stress, leading to inflammation or high levels of stress hormones, which affect the fetus' brain. Another possible explanation holds that parents who abuse children may be mentally ill, which may raise the risk for other mental disabilities, including autism, in relatives, Roberts said.
While provocative, the study results have limitations. First, the data was self-reported. What's more, knowing her child had autism may have influenced a woman's responses to the questionnaires.
One expert worried the findings may fuel parents' fears that they caused their child's condition.
"What is concerning is the potential effect this could have on mothers," said Tanya Paparella, director of the Early Childhood Partial Hospitalization Program at the University of California, Los Angeles, which treats young children who have autism. "We know that autism is strongly genetic in its origin, but we know very little about where the genetic risk factors lie and where the environmental risk factors lie, and very little about the combination of genetic and environmental risks."
Still, the study adds a new piece to the autism puzzle. "We are struggling a little with trying to find out what causes autism," Roberts said. "Our study points to a possible new direction in the research."
The fact that pregnancy-related risk factors for autism were higher in women who were abused "suggests that the effect of abuse can reach across generations," Roberts added. "As a society, we need to focus more on how children are cared for and give more support to families who might be at risk for abusing their children."
The study is published online today (March 20) in the journal JAMA Psychiatry.
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