Study Reveals Genetic Risk Factors Associated with ADHD
12 regions in the human genome are associated with ADHD, according to a new ground-breaking study. Understanding the genomic underpinnings of the condition may, researchers say, vastly improve symptom diagnosis and treatment for patients who exhibit either inattentive or hyperactive/impulsive symptoms at any age.
February 8, 2019
Is attention deficit disorder (ADHD or ADD) associated with a unique set of genetic risk factors? Do signs of ADHD appear in predictable genomic locations in a person’s DNA? Can DNA analysis help to determine whether ADHD is at play? Last Fall, an international team of researchers led by the Psychiatric Genomics Consortium of Great Britain’s Cardiff University began to answer these important and complicated questions by discovering the first-ever set of common genetic risk factors associated with ADHD.
In what amounts to the largest genetic study of ADHD to date, the Cardiff group analyzed genetic information from more than 20,000 people with ADHD and more than 35,000 people without ADHD. And this survey data revealed something remarkable: 12 genomic regions, or “loci,” where people with ADHD differed from their non-ADHD peers. Several of these 12 regions are in or near genes with a known relationship to the processes involved in healthy brain development.1
“This group of common genetic risk factors, contributes about 22% to the risk of ADHD,” says Dr. Joanna Martin, a research associate based at Cardiff’s MRC Centre for Neuropsychiatric Genetics and Genomics. “This study is a very important step toward understanding the genetic and biological underpinnings of ADHD, as it is the first study to robustly detect commonly occurring genetic risk factors. The results of the study will enable a lot more research into the causes of ADHD, which has the potential to lead to better future treatments and diagnosis of affected individuals.”
“This is the first genome-wide search that has found loci [locations in the genome] associated with ADHD at a level that is considered to be statistically significant,” adds Dr. Thomas Fernandez, of Yale University’s Child Study Center.
Dr. Fernandez points out that the study is also significant because “it shows that we now have crossed the ‘tipping point’ for the number of research subjects required to begin discovering significant genetic loci in ADHD.” In addition, as researchers add more subjects to the study, more loci will be discovered, which could then pave the way for more genetic tests informing diagnosis and treatment selection.
“Furthermore,” he continues, “by doing a ‘deep dive’ into the loci that are identified as significant, we can learn more about the underlying biological mechanisms at play in ADHD.”
“The sophisticated methodology, including replication with different samples, will inform the design of future studies,” says Dr. Mark Stein, a professor of psychiatry and principal investigator at the Center for Child Health, Behavior and Development at the Seattle Children’s Hospital, “which will bring us a step closer to understanding ADHD risk and the potential for preventive and therapeutic advances.”
The study, which brought together groups from Europe, North America, and China, as well as researchers from Denmark and Australia, “supports previous research showing that clinically diagnosed ADHD appears to be the extreme end of a continuous distribution of traits of hyperactive, impulsive, and inattentive problems in the general population,” says Dr. Martin. “This suggests that the findings of this and other genetic studies of ADHD may also be relevant to people who have traits of ADHD that are not at clinically diagnostic levels.”
The size and breadth of the study should also lead to further studies and higher levels of participation in studies of this kind.
Dr. Martin says that the next step is to determine the exact role of the identified genes in developing ADHD symptoms. Knowing that should lead to better ADHD evaluations and treatments. “This is further evidence that ADHD is a complex biological condition,” adds Dr. Martin, who believes that the study will help “increase understanding, reduce stigma and eventually lead to a better understanding of possible causes and treatments of ADHD.”
1 “Discovery of the first genome-wide significant risk loci for attention deficit/hyperactivity disorder,” Cardiff University. Nature Genetics (January 2019). https://www.ncbi.nlm.nih.gov/pubmed/30478444