Canadian researchers have become the first to pinpoint specific behavioral signs in infants as young as 12 months that can predict, with remarkable accuracy, whether a child will develop autism.

The preliminary findings, published this month in the International Journal of Developmental Neuroscience, were taken from an ongoing study of 200 Canadian infants, the largest study of its kind in the world. The infants, many of whom have been followed from birth to 24 months, are younger siblings of children who have been diagnosed with autism.

Studies show that families with one autistic child have a roughly five to10 percent chance of a second child being diagnosed with autism, a rate of recurrence about 50 times higher than the general population.

The Canadian study, which began as a collaboration of McMaster University's

Offord Centre for Child Studies in Hamilton, The Hospital for Sick Children in Toronto and the IWK Health Centre in Halifax, has gained international attention. Initially funded by The Hospital for Sick Children Foundation, and currently by the Canadian Institutes of Health Research (CIHR), it has mushroomed into a global initiative involving leading autism researchers in 14 cities across Canada and the U.S.

Chaired by Lonnie Zwaigenbaum, a developmental pediatrician with the Offord Centre and McMaster Children's Hospital and a lead investigator for the Canadian study, the Canada - U.S. Baby Sibs Research Consortium is supported by the National Alliance for Autism Research (NAAR) and the National Institute of Child Health and Human Development (NICHD) in the U.S. It is widely regarded as one the most exciting developments in autism research today.

"This is groundbreaking work that is pushing the frontier of what we know about the biological nature of autism, and why it emerges so early in life," says Dr. Zwaigenbaum. "Our hope is that it will lead to the development of new and earlier treatments that could make a huge difference for these children."

Second only to mental retardation as the most common developmental disability, autism forms part of a spectrum of related disorders referred to as the autism spectrum disorders (ASDs). Although symptoms can range from mild to severe, those affected typically exhibit severe impairments in social interaction and communication, and engage in repetitive, solitary activities.

The complex nature of the disorder makes it difficult to diagnose. In the absence of any biological marker, clinicians have been typically forced to rely on parental reports, home videos and direct observations of behavior, using standardized tools like the Checklist for Autism in Toddlers (CHAT). But these tools were designed for children 18 months and older; there has been no instrument to measure autistic behaviors in young infants.

So the Canadian researchers designed their own. Led by Susan Bryson, Craig Chair in Autism Research at the IWK Health Centre/Dalhousie University, and co-lead investigator for the study, they developed the Autism Observation Scale for Infants (AOSI). The scale maps the development of infants as young as six months against 16 specific risk markers for autism, including such behaviors such as not smiling in response to the smiles of others or not responding when one's name is called.

"The predictive power of these markers is remarkable", says Dr. Zwaigenbaum. "We are finding that within this high-risk group of siblings, almost all of the children who are diagnosed with autism by age two years have seven or more of these markers by the time they are a year old."

The researchers found that even at six months of age there were certain behaviors that distinguished those siblings later diagnosed with autism from other siblings. These included a passive temperament and decreased activity level at age six months, followed by extreme irritability, a tendency to fixate on objects, reduced social interaction and lack of facial expression as they approached the age of 12 months. At one year, these same children also showed difficulties with language and communication – they used fewer gestures, understood fewer phrases and had lower scores for both expressive and receptive language.

It is not known whether these risk markers constitute an early manifestation of the disorder, or are behaviors that reduce the child's opportunities to learn from social experiences, thereby contributing to a pattern of development that may lead to autism. Still, the results shed new light on when autism starts and how early it can be detected.

"This is an important breakthrough in our understanding of the initial behavioral signs of autism," says Peter Szatmari, Director of the Offord Centre and a member of the Canadian research team. "By identifying these signs in children as soon as they are detectable, clinicians will be able to diagnose earlier, interventions can begin earlier, and we can improve the long-term outcomes for these children."

Jessica Brian, who with Wendy Roberts is one of two investigators at The Hospital for Sick Children working on the study, has already developed and begun to evaluate innovative interventions for infants showing early signs.

John Kelton, dean and vice-president of McMaster's Faculty of Health Sciences, said: "This is an important step forward. The team at the Offord Centre is making a real difference towards better care for children and families affected by autism."