Environmental Factors More Important Than Realized in Autism Development

It's not just genes that influence whether or not a child develops autism, it's also environment. Now, scientists have taken a closer look and have found that environmental factors are far more important than previously thought.

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder that's defined by impairments in social interaction and communication. It's often associated with the presence of restrictive and repetitive behaviors. While the actual cause of autism is known, it's thought to develop through both environmental and genetic factors.

In order to get a better understand of this disorder, the researchers looked at over 2 million people using national health data registers. About 14,156 of the children examined had a diagnosis of ASD, and the study itself involved two measures of autism risk. The researchers took heritability into account and relative recurrent risk in account; this measures individual risk for people who have a relative with autism.

"Heritability is a population measure, so whilst it does not tell us much about risk at an individual level, it does tell us where to look for causes," said Avi Reichenberg, one of the researchers, in a news release. "We were surprised by our findings as we did not expect the importance of environmental factors in autism to be so strong. Recent research efforts have tended to focus on genes, but it's now clear that we need much more research to focus on identifying what these environmental factors are. In the same way that there are multiple genetic factors to consider, there will likely be many different environmental factors contributing to the development of autism."

The findings reveal that it's possible to potentially help reduce environmental risks to lower the risk of autism in children. Now, the task will be identifying what these environmental risks might be in order to take preventative measures.

"Our study was prompted by a very basic question which parents often ask: 'if I have a child with autism, what is the risk my next child will too?'" said Sven Sandin, one of the researchers, in a news release. "Our study shows that at an individual level, the risk of autism increases according to how close you are genetically to other relatives with autism. We can now provide accurate information about autism risk which can comfort and guide parents and clinicians in their decisions."

The findings are published in the journal JAMA.