Women abused in childhood are more likely to have children with autism, a new epidemiological study suggests. The finding adds a disturbing new dimension to the heated debate over the condition’s underlying causes.

Andrea Roberts of the Harvard School of Public Health suspected that there might be a link between childhood abuse and having an autistic child: women abused early in life are more likely to smoke, suffer from gestational diabetes and have premature babies – all factors that may affect fetal brain development.

To investigate, Roberts and her colleagues turned to the Nurses’ Health Study II, which includes almost 55,000 women who had indicated if they had a child with autism spectrum disorder and also answered a questionnaire about their experience of abuse as a child. This allowed the researchers to develop a scale rating all the women for the intensity of abuse in their childhood.

There was a clear link between the “dose” of abuse received and the risk of having an autistic child. “The associations get stronger as the level of abuse increases,” Roberts says.


Big surprise

After accounting for demographic factors such as age and socioeconomic status, the 2 per cent of women who reported the most serious childhood abuse – who were frequently hit and also sexually abused – were about 3.5 times as likely to have a child with autism as those who reported no abuse at all.

“I think it’s a really interesting, innovative and well-conducted study,” says Hannah Gardener at the University of Miami in Florida. “There aren’t a lot of risk factors with that magnitude.”

The elevated risk extended over a surprisingly large number of women. For the top 25 per cent of women on the childhood abuse scale, the risk of having a child with autism was increased by 60 per cent compared with women who reported zero abuse.

However, the biggest surprise came when the researchers looked at nine pregnancy-related factors that might explain the link – including smoking and gestational diabetes. These accounted for only about 7 per cent of the increased risk. “They explain very little of our findings,” says Roberts.

Life-long stress

What else might be going on? One possibility is that women who experience abuse undergo “epigenetic” modifications to their DNA, which affect gene activity and may be passed onto their children. Alternatively, Roberts suggests that abuse as a child may alter a woman’s stress responses, perhaps causing inflammation that could harm the developing brain of a fetus.

“My first thought was stress and anxiety in women that extends throughout their lives,” agrees Gardener. “It highlights the fact that the effects of abuse on children are really quite varied and long-lasting.”

However, Gardener emphasises that autism remains a relatively rare condition, and she hopes that the new findings do not make women who were abused as children think twice about having children of their own. Even among the highest-risk group in the new study, less than 1 in 50 of the women who became mothers had a child with autism.

Journal reference: JAMA Psychiatry, doi.org/kv9