Children with autism whose parents participated in an intervention and studied their interactions with them between the ages of two to four showed less severe symptoms of autism as they aged, according to a new study published in The Lancet.

People who have been diagnosed with autism typically struggle with communication and face social and behavioural challenges. According to Autism Speaks Canada, symptoms generally tend to show in children between the ages of two and three, and affect tens of millions around the world.

The study was a follow-up to the Preschool Autism Communication Trial, which had parents record their conversations with children. The newest study was aimed at evaluating the long-term effects of the trial.

The Preschool Autism Communication Trial was conducted in 2010 and spread over the course of one year.

The trial had 12 therapy sessions held over the course of the first six months followed by monthly support sessions for the remaining six months.

Parents would record their interactions with their children and then study the videos with therapists, who would advise them on how to better interpret their child's indirect and unusual communication.

Researchers from the University of Manchester, King's College London and Newcastle University studied the participants six years after the trials ended.

"The results of our investigation show a treatment effect to reduce autism symptom severity at treatment endpoint, which remained almost 6 years later," researchers concluded in their report. "Taken together, these results are encouraging and provide evidence that sustained changes in autism symptoms can be possible after early intervention, something that has previously been regarded as difficult to achieve."

Professor John Green from the University of Manchester, the lead researcher in the study, says having parents involved impacts the day-to-day life of the child more than traditional treatment with the help of a therapist.

"This is not a 'cure,' in the sense that the children who demonstrated improvements will still show remaining symptoms to a variable extent, but it does suggest that working with parents to interact with their children in this way can lead to improvements in symptoms over the long-term," he said in a release.

Parents who participated in the recorded interactions say their children had improved relationships with other children, as well as better social communication and a reduction in repetitive behaviours.

Researchers found the children who had participated and suffered from severe autism symptoms saw a 17-per-cent reduction in their severity.

However, the researchers noted that there was no evidence of the trials having any effect on the child's mental health.

"Additional interventions may be needed to address these difficulties at later ages," said Professor Tony Charman, who led the London aspect of the study, and Professor Andrew Pickles, the study's methodology expert, in a joint statement. "As these children grow up, they will continue to need support in many aspects of their lives. We are currently working to further enhance our intervention."

The researchers do caution that the findings don't provide information in how the symptoms will develop in adulthood.