By Steven Reinberg
Millions of American children with Attention Deficit Hyperactivity Disorder (ADHD) may have a genetic vulnerability to the disease, according to a new study.
The researchers analyzed data from more than 55,000 people and identified 12 gene regions associated with ADHD. These areas may affect the central nervous system. The discovery could help scientists develop new therapies for ADHD, which affect more than 9 percent of American children.
"We all carry genetic variants of risk for ADHD," explained Anders Borglum, a professor of bio-medicine at Aarhus University in Denmark. "The more we have, the greater the risk of developing ADHD."
The same genetic regions are associated with 200 diseases and other features, he said. The researchers also found that 44 genetic variants involved in ADHD are associated with depression, anorexia and insomnia.
"Now we understand better why some people develop ADHD, and begin to gain insights into basic biology, paving the way for a new and better treatment of ADHD," added Borglum.
The genetic areas that his team has uncovered show that this is mainly a brain disorder, Borglum said.
The researchers also found genes that may be associated with ADHD have a role in how brain cells interact and also influence speech development, learning and regulation of dopamine (a chemical messenger that leads to signals between brain cells).
However, the vast majority of ADHD genetics has yet to be exposed and will require larger studies, Borglum said.
Research author Stephen Parona noted that the team "found 12 of very many – we do not know how many – probably thousands of genes associated with ADHD." Faraone is Professor of Psychiatry and Behavioral Sciences at SUNY Upstate Medical Syracuse, NY.
The researchers do not expect to discover only one, two, or even 10 genes, each of which has a dramatic effect on ADHD and can be used to diagnose the disorder or develop treatment quickly. Most likely, a combination of genes and environmental factors cause ADHD, study authors.
Environmental factors may include premature birth and underweight or developmental problems, such as fetal alcohol syndrome, Faraone said.
Interestingly enough, although the drugs work in the treatment of ADHD, they are not directed at the genes researchers have found related to its condition. None of the genes affected by the drugs appeared in the analysis of their genes associated with ADHD, Faraone said.
The report was published online November 26 in the journal Nature Genetics.
Ronald Brown, dean of the School of Health Sciences at the University of Nevada in Las Vegas, said: "This is a promising investigation, as it indicates that Attention Deficit Hyperactivity Disorder is a hereditary disorder." Brown was not involved in the study, but he knew the findings.
It has been clear for years that ADHD runs in families, he said. These findings are also important because they suggest that certain treatments that are effective for one family member may be effective for other family members who have been diagnosed with ADHD.
This study is also important because it shows that a number of psychological disorders are probably related to these genes, although no association between cause and effect has been established in the study. This information can help families with early prevention and intervention efforts, Brown said.