Scientists at the University of Edinburgh and the Queensland Institute for Medical Research report that genes linked with a greater risk of developing autism may also be associated with higher intelligence. They say they also found new evidence linking genetic factors associated with autism to better cognitive ability in people who do not have the condition.
Nevertheless, the relationship between autism and intelligence is not clear, add the researchers. Although up to 70% of individuals with autism have an intellectual disability, some people with the disorder have relatively well-preserved, or even higher than average, non-verbal intelligence, the team adds.
Autism is a developmental disability that can cause significant language and speech difficulties. Non-verbal intelligence enables people to solve complex problems using visual and hands-on reasoning skills requiring little or no use of language.
The scientists analyzed almost 10,000 people recruited from the general population of Scotland. Individuals were tested for general cognitive ability and had their DNA analyzed. The team discovered that even among people who never develop autism, carrying genetic traits associated with the disorder is, on average, linked to scoring slightly better on cognitive tests. The researchers found further evidence of a link between autism-associated genes and intelligence when they carried out the same tests on 921 adolescents who were part of the Brisbane Adolescent Twin Study (BATS).
“We report that polygenic risk for ASD is positively correlated with general cognitive ability, logical memory and verbal intelligence in GS:SFHS [Generation Scotland Scottish Family Health Study],” wrote the investigators in their study (“Common polygenic risk for autism spectrum disorder [ASD] is associated with cognitive ability in the general population”) in Molecular Psychiatry. “This was replicated in BATS as a positive association with full-scale intelligent quotient.”
According to Toni-Kim Clarke, M.D., of the University of Edinburgh's division of psychiatry, who led the study, “Our findings show that genetic variation which increases risk for autism is associated with better cognitive ability in non-autistic individuals. As we begin to understand how genetic variants associated with autism impact brain function, we may begin to further understand the nature of autistic intelligence.”
“Links between autism and better cognitive function have been suspected and are widely implied by the well-known `Silicon Valley syndrome’ and films such as 'Rain Man’ as well as in popular literature,” notes Nick Martin, Ph.D., of the Queensland Institute for Medical Research. “This study suggests genes for autism may actually confer, on average, a small intellectual advantage in those who carry them, provided they are not affected by autism.”