The researchers analyzed the DNA of 8,862 Scottish people from the Generation Scotland: Scottish Family Health study. These participants completed four cognitive tests: the Mill Hill vocabulary scale junior and senior synonym tests, a verbal declarative memory test, the Weschler digit-symbol substation task, and a verbal fluency test. The researchers calculated an overall intelligence score based on their test performance. Then, they evaluated the connection between the intelligence scores and how high the participants’ genetic risk for ASD or ADHD was.
This cross-sectional analysis was controlled for age and gender variables. The researchers conducted similar analyses on two smaller samples to confirm their findings.
Genes related to ASD were linked to slightly higher cognitive scores, but genes related to ADHD were not associated with any trends in cognitive performance. The researchers found that less than 0.5 percent of the difference in cognitive scores could be explained by how many ASD-related gene variants a person had.
The study raises questions around ASD and cognition. Around 70 percent of people with ASD have below-average intelligence. Yet, according to the study, genes associated with ASD were related to slightly higher intelligence in the general population. It is not clear why this discrepancy exists. The results are a first step in investigating the relationship between ASD and intelligence.
This research is published in the journal Molecular Psychiatry.
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