The number of kids diagnosed with autism has continued to climb, and 2 percent of American children ages 6 to 17 have received the diagnosis, according to parent surveys collected in 2011 to 2012 by the federal Centers for Disease Control and Prevention. That’s quite a dramatic increase from the 1.2 percent of children reported in parent surveys conducted in 2007, and the CDC said the recent rise was greatest in boys and included cases that might previously have not been diagnosed.
“Those who were first diagnosed in or after 2008 were more likely to have milder autism spectrum disorder than those diagnosed in or before 2007,” wrote CDC officials in their report released on Wednesday.
Increased awareness and medical coverage for autism have no doubt contributed to the uptick in diagnoses—especially for borderline cases that barely meet the criteria for being on the spectrum. “Kids with social problems who wouldn’t have necessarily been diagnosed with autism in the past are nowadays getting the diagnosis, so it’s tough to tell how much the prevalence is truly increasing,” said Dr. Andrea Roberts, a research associate at the Harvard School of Public Health.
Roberts and other autism researchers have compiled a list of lifestyle and environmental factors that appear to increase a child’s risk of developing autism, usually due to their parents’ or even grandparents’ experiences.
In a study published in JAMA Psychiatry on Wednesday, Roberts and her colleagues examined medical records from 50,000 women enrolled in the Nurses’ Health Study II and found that those who experienced the most physical, emotional, or sexual abuse as children were 60 percent more likely to have a child with autism; 1.8 percent of children born to women reporting the highest amount of abuse had autism compared with 0.7 percent of those born to women who said they were never screamed at, hit, or sexually abused as children.
“One in four women in our study fell into that top group of women who suffered the most abuse, which is a lot of people,” Roberts said. These women were also more likely to have other factors that have been shown in previous research to increase a child’s autism risk: they were more likely to smoke, be overweight, and take antidepressants during pregnancy than those who reported no abuse. But Roberts said these differences accounted for only a small part of the increased autism risk.
“Perhaps abuse has lasting effects on a women’s immune system or her stress response system that might be increasing their child’s risk in utero,” Roberts said. Excess stress hormones, for example, could constrict blood flow to the fetus, impairing brain development.
This study doesn’t prove that abuse in childhood leads to more autism but merely makes the association. Likewise another study in the same journal found that a grandfather’s age when he fathered his children may have something to do with his grandchild’s autism risk. It, too, doesn’t prove a cause and effect but it makes an interesting association.
Men who had fathered a daughter when they were 50 years or older were nearly 80 percent more likely to have a grandchild with autism than those who conceived the child in their early 20s. Those who fathered sons at this older age were 67 percent more likely than younger fathers to have a future grandchild with autism.
While there’s nothing prospective parents can do about the age of their father when they were born or abuse suffered in childhood, women who suffered abuse can take measures that might help reduce any increased autism risk they may face during pregnancy. Roberts recommended exercise and meditation to help manage stress—which is good advice for all pregnant women. Professional counseling may also be beneficial to help women come to terms with their past abuse and also to ensure that they will be better parents than their own parents were.