Has there been a true increase in autism prevalence? At first look, the numbers suggest a rapid increase, but at least some of that change reflects greater awareness and shifting diagnostic criteria.Some research suggests that there has been no true increase at all. The Pittsburgh Post-Gazette reports on the controversy:
David Amaral leans the other way. Noting that the rates of other immune disorders like asthma, multiple sclerosis and rheumatoid arthritis also are going up in America, he postulates that something in the environment may be triggering immune reactions that could play a part in autism.
"I believe there are environmental factors [that play a role], and I think we have to stay open to whatever influences there might be and be willing to explore them."
When Nancy Minshew of the University of Pittsburgh sorts through all the evidence, though, she thinks it's likely autism rates have been steady for generations.
"I tend to think [the increase] is the result of people recognizing that you can have autism and be verbal and can have above-average intelligence, and in the past those people who were verbal and particularly those who seemed so smart but could never hold a job, they got diagnosed with schizophrenia or a variety of other disorders," said Dr. Minshew, who directs Pitt's Center for Excellence in Autism Research.
In past decades, people with severe autism also were often put in institutions or kept at home, she added.
Because of that, Americans now in their 40s and older grew up without seeing many people with debilitating autism, she said. "To them, it never existed. Autism was never diagnosed, but that doesn't mean it wasn't there, but their perception was that it didn't exist."
So when older Americans look around today at all the families they know with autistic children, they see a surge in the numbers.
Dr. Minshew said she still encounters older adults who are autistic, but never received that diagnosis. "The typical adult I see who has autism spectrum disorder has about seven different past diagnoses, none of which quite fit -- OCD [obsessive-compulsive disorder], bipolar, depression. People who don't know about autism gave them a diagnosis based on some feature that looked familiar to them."