Summary: The genes that underlie aggression in ADHD and disruptive behavioral disorders are the same genes that affect aggression in the general population.
Source: Aarhus University
An international collaboration headed by researchers from iPSYCH has found genetic variants that increase the risk of aggression in children with ADHD. In the same study, the researchers also discovered that the genetics which increase aggression in some children with ADHD, are the same genetics that affect aggression in children without a diagnosis.
For the first time, researchers have found positions in the genome that increase the risk of getting ADHD with disruptive behaviour disorders (DBDs). DBDs are child psychiatric disorders characterised by antisocial and aggressive behaviours. The findings have been made by the Danish iPSYCH consortium and the Psychiatric Genomics Consortium.
The results can be used to gain an understanding of the biology that leads to ADHD with DBDs, which 20-30 per cent of children with ADHD have.
The researchers analysed the genome from 3,802 children with ADHD and DBDs and 31,305 without and identified three specific locations in the genome that increase the risk of having ADHD with DBDs. One particular genetic variant located on chromosome 11 increases the risk of seems to specific to the aggressive behaviour.
The new study also show that the aggressive behaviour in children with ADHD and DBDs in part can be explained by genetics.
“We’ve also compared our results with results from another large genetic study of aggression in children who do not have a child psychiatric disorder. We discovered that the genetics involved in ADHD with DBDs to a great extent is shared with the genetics involved in aggression in the general population,” says Ditte Demontis, who is one of the researchers behind the study. She is associate professor at Aarhus University and part of the iPSYCH research project, which is where a major part of the data used in the study comes from.
“In other words the genetics that affect aggression in children with ADHD with DBDs are the same as the genetics that underlie aggression in general. Children with ADHD with behavioural disorders have been unlucky and have received many of the genetic variants that increase the risk of aggressive behaviour,” says Ditte Demontis.
The results have been published in the scientific journal Nature Communications.
“The results of our study have revealed a small part of the biological mechanisms in the body involved in ADHD with DBDs,” says Ditte Demontis.
ADHD and DBDs are both complex disorders in which both environment and genetics affect the risk.
“The genetic risk is comprised of many genetic variants, each of which increases the risk slightly. This means that the genetic variants we have identified in this study only represents the tip of the iceberg,” says Ditte Demontis, and emphasises that this is only the first step on the road towards fully understanding the biological mechanisms underlying ADHD with DBDs.
The research results – more information
The study is a genome-wide association study. That is to say, a study in which genetic variants distributed across the entire genome (more than eight million genetic variants in each person) are analysed in order to identify variants that are over-represented in people with ADHD with DBDs compared with people who do not have the disorders.
Risk variants and polygenic architecture of disruptive behavior disorders in the context of attention-deficit/hyperactivity disorder
Attention-Deficit/Hyperactivity Disorder (ADHD) is a childhood psychiatric disorder often comorbid with disruptive behavior disorders (DBDs). Here, we report a GWAS meta-analysis of ADHD comorbid with DBDs (ADHD + DBDs) including 3802 cases and 31,305 controls. We identify three genome-wide significant loci on chromosomes 1, 7, and 11.
A meta-analysis including a Chinese cohort supports that the locus on chromosome 11 is a strong risk locus for ADHD + DBDs across European and Chinese ancestries (rs7118422, P = 3.15×10−10, OR = 1.17). We find a higher SNP heritability for ADHD + DBDs (h2SNP = 0.34) when compared to ADHD without DBDs (h2SNP = 0.20), high genetic correlations between ADHD + DBDs and aggressive (rg = 0.81) and anti-social behaviors (rg = 0.82), and an increased burden (polygenic score) of variants associated with ADHD and aggression in ADHD + DBDs compared to ADHD without DBDs.
Our results suggest an increased load of common risk variants in ADHD + DBDs compared to ADHD without DBDs, which in part can be explained by variants associated with aggressive behavior.