As the reported incidence of autism spectrum disorder (ASD) has risen over the years—in the U.S. it is now estimated by the Centers for Disease Control to affect one child in 59—so has the pace of research to determine its causes and find effective treatments.

Because of the great interest in autism’s origins and how the illness affects children, comparatively less research has focused on the way ASD affects adults. With this in mind, a team of scientists set out to comprehensively review published, peer-reviewed papers that measured the impact of ASD on both social and non-social cognitive functioning in adult patients.

The results, published January 2, 2019 in the journal JAMA Psychiatry, are based on data from 75 papers in which a total of 3,361 adults with ASD were studied alongside a total of 5,344 unaffected adults. This enabled the team to identify areas of cognition in which adult ASD patients are strongest and weakest.

“Our findings support the idea that ASD is not characterized by one ‘primary’ cognitive deficit but instead on a selective range of ‘higher-order’ cognitive abilities,” wrote the team, led by Tjasa Velikonja, Ph.D., of the Icahn School of Medicine at Mount Sinai. She was joined by 2018 BBRF Young Investigator Eva Velthorst, Ph.D., also of Mount Sinai, and 2015 BBRF Young Investigator Anne-Kathrin Fett, Ph.D., of the City University of London, UK.

Their analysis revealed that while there was no significant difference between the adult ASD patients and controls in terms of IQ, among those with ASD there were "medium to large" deficits observed in four key areas of social and non-social cognition. Deficits in social cognition were most notable in the perception and processing of emotions, and in what researchers call “theory of mind”—the ability to attribute mental states, beliefs, and intents to oneself and others.

Significant non-social deficits were also seen in the adults with ASD—in mental processing speed and in verbal learning and memory. These issues could open up possibilities for therapy and rehabilitation, the researchers suggest. Similar deficits are also seen in people diagnosed with schizophrenia, although in adults with ASD they tend to be less severe, they say. “This implies that cognitive training strategies shown to be effective in schizophrenia could also be adopted for the adult ASD population. More research should focus on evaluating the effectiveness of cognitive remediation” in such patients, they write.

Compared with studies of ASD in children and adolescents, the new study suggests that impairments in working memory and verbal fluency “appear to be less pronounced in adulthood. In contrast, cognitive deficits in mental flexibility and response inhibition [i.e., executive control] seem to be large” in adult patients compared with young ones.

The researchers speculate that ASD affects different aspects of cognition differently at different stages of life, with at least some cognitive skills such as verbal fluency delayed initially but eventually catching up with those in adults without ASD. Further studies will be needed to verify this.