A lot of children who had been diagnosed with autism at a young age do not display symptoms any longer when they are older, reveal researchers.
In a study, they found one-third of youngsters who had ever been diagnosed with an autism spectrum disorder no longer had the diagnosis at the time their parents were surveyed, the Daily Mail reported.
The researchers noted that past studies have also found some children who originally have an autism spectrum disorder eventually lose that diagnosis and are no longer considered autistic.
However, whether this is due to a mistaken first diagnosis or actual changes taking place in their brains is controversial.
A team, led by Dr Andrew Zimmerman from Massachusetts General Hospital for Children, studied data from a phone survey of 92,000 parents of children aged 17 and younger in the U.S in 2007 and 2008.
In total, 1,366 said their child had a past or current diagnosis of an autism spectrum disorder. In 453 of those cases, children had been diagnosed by a doctor of having a disorder but parents said they didn't have one anymore.
The researchers found children with a learning disability or delayed development were more likely to continue to be classed as autistic. The same was true for older children who also suffered from epilepsy and anxiety.
However, children or teenagers with early hearing problems were less likely to be considered autistic later on.
The team noted that autism tends to go hand in hand with a variety of other mental and behavioural disorders.
They speculated these could complicate the diagnosis, or slow down any improvement in children who do get diagnosed and treated early.
But experts disagree about whether it's possible for kids who are diagnosed correctly with one of the autism-spectrum disorders to improve to the point where they are no longer affected.
"When you're autistic, you're autistic. It's a very stable condition," said Professor Johhn Matson, at Louisiana State University.
He said even when symptoms improve, people with autism have to keep getting treatment and work to maintain that progress.
Dr Zimmerman argued that recognizing autism early and starting treatment can increase the likelihood for real, lasting improvement.
"It's not unusual to see a child start out with more severe autism and then become more moderate and even mild as the years go by. A lot of the kids are improving, and we don't really know why, except we know there's a lot of moldability of the developing brain," he said.
"We think that earlier treatment is essential and there are reasons to think that we can improve the kids. I'm very optimistic," he added.
The study was published in the journal Pediatrics.