A global team of researchers has found the first common genetic risk factors associated with attention deficit hyperactivity disorder (ADHD), a complex condition affecting around 1 in 20 children. Published yesterday in Nature Genetics, the study included an analysis of genetic information from over 20,000 people with ADHD and over 35,000 people without.
"We identified 12 genomic regions at which people with ADHD differed compared to unaffected individuals, and several of these regions are in or near genes with a known relationship to biological processes involved in healthy brain development," says Dr. Joanna Martin of Cardiff University. The genetic risk factors for ADHD also overlapped with risk factors for other psychiatric and physical disorders, including depression, obesity, type 2 diabetes, and lower levels of "good" HDL cholesterol.
The researchers found that diagnosed ADHD appears to share much of the same genetic background as traits associated with ADHD—such as inattention and fidgetiness—that can be measured in the general population. The team compared the genetic risk for diagnosed ADHD with genetic markers associated with traits of ADHD in over 20,000 children and found a high correlation—around 97%—between the two.
"This is a landmark study because it involves patients from all over the world,” says Professor Anita Thapar of Cardiff University. “This large number of patient samples has been lacking for ADHD, meaning our understanding of ADHD genetics has lagged behind physical disorders and other psychiatric disorders like schizophrenia and depression. Thanks in large part to Denmark, this is beginning to change.”
Although the 12 genomic signals identified in this study are important, they capture only around 22% of the risk for ADHD. The roles of other factors, such as rarer genetic changes and environmental factors, will also be important to examine in future research studies.