Sibling Study Bolsters Genetic Link Between Autism, Attention Deficit

Posted on January 23, 2019

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This study was the first of it kind as it analyzed both the conditions of Autism and ADHD simultaneously, two conditions that often co-occur. They also did so in younger siblings where the results showed a significant genetic overlap between both conditions.

Assistant professor of psychiatry and behavioural science at the University of California, Davis Meghan Miller attests to the reliability of this study due to its focus on later born siblings, that enables them to acquire a better sense of the genetic contributions and recurrence risk estimates. This makes it different from previous studies that might present an artificially low recurrence of both ADHD and autism due to ‘stoppage’ which refers to the phenomenon when parents choose not to have more children upon having one diagnosed child.

After analyzing medical records from two large healthcare systems in the United States, what was found was that children who have an older sibling with autism were 30 times more likely of having autism as compared to children with typical older siblings. Similarly, children with an older sibling with ADHD were 13 times more likely of having ADHD. Furthermore, children with older siblings with either condition also more likely to have the other condition such as children with older siblings with autism where 3.7 times more likely to have ADHD, and those with siblings of ADHD were 4 times more likely of having autism. These findings give strong evidence to the familial factor in these neurodevelopmental disorders.

Though these findings are eye opening, the data collected were predominantly white. In generally there are cultural differences with regards to diagnosis of these conditions such as how non-white children were more likely to be diagnosed with ADHD than with autism. Thus, it would be important and interesting for this study to be replicated with a more culturally diverse population.

There may be other genetic factors that affect the development of these neurodevelopmental disorders such as gender and age of mother during pregnancy but ultimately, the findings from this study suggests that doctors should look beyond what condition the older sibling might have when evaluating the younger sibling. Lastly, though the familial factors have been confirmed through this study, the absolute risk of a later-born sibling with either condition is actually small and thus parents should not be overly concern resulting to stoppage.

Category(s):Attention Deficit Hyperactivity Disorder (ADHD), Autism spectrum disorders, Child Development

Source material from Spectrum