The US government estimates that autism is becoming more common, but the increase is small, and some experts think it can be largely explained by better diagnosis.
The causes of autism are not well understood, and it is not clear if other factors might also be at play, for instance, more couples having babies later in life, explained Thomas Frazier, chief science officer for the advocacy organisation Autism Speaks. “There is still a ton of work to do to better understand why this is happening,” Frazier said of the increase.
There are no blood or biological tests for autism. It is identified by making judgements about a child’s behavior. Traditionally, autism was diagnosed only in children with severe language and social impairments and unusual, repetitious behaviors. But the definition gradually expanded, and autism is now shorthand for a group of milder, related conditions.
Heather Cody Hazlett, a University of North Carolina psychologist, researches new ways to do spot autism earlier. What is discouraging, she said, is that fewer than half of autistic children are diagnosed by the time they reach four years old.
There is still a lag between when parents first become concerned and when children are diagnosed. Many doctors may be reluctant to jump to an autism diagnosis in a younger child because they are “trying to be cautious and not alarmist”, Hazlett said. However, delay in diagnosis can lead to a delay in therapy or provision of other services.