Many parents notice signs of autism in their children a long time before an official diagnosis is made, a new study has found.

In some cases, parents pick up on differences when their children are just six months old.

Autism, also known as autism spectrum disorder (ASD), is a biological disorder of the brain that impairs communication and social skills. Signs can include an absence of eye contact, apparent aloofness, avoidance of physical contact even with family, difficulty dealing with interruptions to routine and a lack of interest in other children and what they are doing.

While most children are diagnosed by the age of three, some may be even older. However, according to Canadian researchers, healthcare professionals working in this field would do well to consider the views of parents.

"Parents are the experts when it comes to their kids and their observations are really valuable. In some respects, parents are picking up on differences at six and nine months of age that we have a much harder time seeing in the clinic," commented Lonnie Zwaigenbaum, co-director of the University of Alberta's autism Research Centre.

He and his colleagues assessed the reported concerns of the parents of around 300 families with young children, over a 12-year period. These families included parents who did not have any increased concerns about autism, and families who did, such as those who already had children diagnosed with autism.

At three years of age, all of the children who the parents were concerned about underwent a clinical assessment for autism. The researchers then looked back at the concerns the parents of these children had over the years.

"We found that parents whose children ended up being diagnosed at three years of age did report more concerns. Interestingly, they reported sensory and motor concerns starting at the age of six months. And then they increasingly reported more language and social concerns at about 12-15 months of age. It really highlights the importance of talking to parents and taking their concerns seriously," they said.

They suggested that if healthcare professionals acted on parents' concerns earlier, children at risk of autism could receive better care.

"Where interventions are concerned, the earlier you can start with the patients, the better the prognosis is. If you can identify a child at a heightened risk earlier, before their first birthday, then you can start working with them to address early developmental difficulties, which can ultimately enhance their skill development and improve their outcomes," the researchers added.

Details of these findings are published in the Journal of the American Academy of Child & Adolescent Psychiatry.