A simple change in the order of questions asked to parents has nearly doubled the estimated rate of U.S. children with autism to 2.24%, federal researchers suggested in a report on Friday.
Autism is characterized by social and behavioral challenges in childhood. Rather than an alarming rise in diagnoses of the syndrome, the new numbers from the National Health Interview Survey — up from 1.25% of kids in 2013 — better reflect estimates found in other surveys, say the researchers from the National Center for Health Statistics.
It’s unlikely that the increase is due to a change in some kind of environmental risk factor.
“[T]rue year-to-year changes of the magnitude observed are unusual,” wrote the NCHS research team, led by Benjamin Zablotsky.
The survey, given by in-person interviewers to 13,000 parents in 2014, swapped the order in which parents were asked whether their child had ever been diagnosed with an autism disorder. Surveys in earlier years had first asked whether they had been diagnosed with any developmental disorder, and then asked about autism on a menu of more specific diagnoses. The 2014 survey asked about autism first, before asking about other developmental disorders.
The change in question order essentially meant parents were asked about “a different concept” of autism than in previous years, the statistics experts said, potentially making them more likely to accurately report their children’s diagnoses.
Overall, nearly 6% of all children in the U.S. suffer from an intellectual or developmental disability, according to the survey, numbers that have held steady with previous years and reflect other estimates.
Autism diagnoses have steadily increased over the last two decades, starting from around 0.1% of children from a 1997 survey, the first in which the Census Bureau collected information about childhood developmental disabilities.