The 5 novel loci identified associated with ADHD provide evidence for a shared genetic basis between ADHD and educational attainment.
Alexey A. Shadrin, PhD
A recent study in The Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP) suggests that educational under-attainment may share some of the same genetic underpinnings as attention deficit hyperactivity disorder (ADHD).
"It is already known that individuals with ADHD tend to have academic underachievement," Alexey A. Shadrin, PhD, postdoctoral research fellow at the Norwegian Centre for Mental Disorders Research (NORMENT), and first author of the study, told MD Magazine. "Our study suggests that this tendency, at least partly, may be attributed to genetic risk."
ADHD appears to be highly heritable, but little is known about the specific genes that underlie the disorder. Twin and family studies have implied a link, but a 2010 meta-analysis from the psychiatric genomics consortium — a group of researchers around the world dedicated to producing meta-analyses on genes for disorders such as ADHD and autism — wasn’t able to produce strong gene candidates.
Shadrin and his team at NORMENT, recently developed a statistical framework that allows them to analyze overlapping genes in 2 different traits. They've previously used the tool to study mental disorders such as schizophrenia and bipolar disorder, but didn't have access to data they thought would properly overlap with and allow them to study ADHD. While there is some existing data on genes for ADHD, they also need large trove of data on another trait that was likely to overlap with data.
Then, in 2016, the Social Science Genetic Association Consortium published a study on educational attainment. The study included information about the genes of 300,000 individuals with educational under-attainment.
Educational under-attainment is 1 of the hallmarks of ADHD, and can have profound, long-term impacts on a patient's life. Suspecting that there'd be significant overlap between genes associated with educational under-attainment and ADHD, the team used their tool to study the data from the 2016 study, along with the data from the Psychiatric Genomics Consortium, the largest study of ADHD-related genes, which included 3,000 participants with ADHD.
They found 5 novel genetic loci for ADHD, 3 of which were also associated with educational under-attainment. They also found a clear negative correlation between genes associated with ADHD and genes associated with educational attainment.
The results point to a shared genetic basis for both ADHD and educational under-attainment.
"The findings emphasize the need for identifying and helping children with ADHD in the school setting," Shadrin explained.
Nonetheless, effect size was small, and the information can't be used for clinical diagnosis or to guide treatment. Future studies will need to explore the mechanisms in how these genetic risks exert their effects in the pathogenesis of ADHD. Additionally, while the study identified a few genes associated with ADHD, scientists believe there are hundreds more to be identified.
The study, "Novel Loci Associated With Attention-Deficit/Hyperactivity Disorder Are Revealed by Leveraging Polygenic Overlap With Educational Attainment" was published in The Journal of the American Academy of Child and Adolescent Psychiatry in the February 2018 issue.
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