Inherited Structural Gene Variations Play an Important Role in ADHD Development
ADHD is known to be strongly influenced by genetics, but specific genetic factors underlying the risk for ADHD have eluded researchers. Now research published in the June 2009 advance online publication of Molecular Psychiatry identifies hundreds of gene variations that occur more frequently in children with ADHD as compared to children without ADHD. Many of those genes were already known to be important for learning, behavior, brain function and neurodevelopment, but had not been previously associated with ADHD.
"Because the gene alterations we found are involved in the development of the nervous system, they may eventually guide researchers to better targets in designing early intervention for children with ADHD," said lead author Josephine Elia, M.D., a psychiatrist and ADHD expert at The Children's Hospital of Philadelphia.
This study is the first to investigate the role of CNVs (copy number variations – missing or repeated stretches of DNA) in ADHD. We all have CNVs in our DNA, but not all the variations occur in locations that affect the function of a gene.
"When we began this study in 2003, we expected to find a handful of genes that predispose a child to ADHD," said study co-leader Peter S. White, Ph.D., a molecular geneticist and director of the Center for Biomedical Informatics at Children's Hospital. "Instead, there may be hundreds of genes involved, only some of which are changed in each person. But if those genes act on similar pathways, you may end up with a similar result—ADHD. This may also help to explain why children with ADHD often present clinically with slightly different symptoms."
“As we delve into the genetics of very complex diseases such as ADHD, we find many contributing genes, often differing from one family to another," added White. "Studying the functions of different genes allows us to identify biological pathways that may be involved in this neuropsychiatric disorder."
In addition, as we learn more about specific genes involved in ADHD, the hope is that researchers may eventually be able tailor treatments to an individual’s own genetic profile, to achieve more effective therapies. Elia and White stress, however, that much more work must be done before genetic findings lead to ADHD treatments.
Elia et al, "Rare Structural Variants Found in Attention-Deficit Hyperactivity Disorder Are Preferentially Associated with Neurodevelopmental Genes," Molecular Psychiatry, published online, June 23, 2009.
Children's Hospital of Philadelphia. “ADHD Genes Found; Known to Play Roles in Neurodevelopment -- Missing DNA Segments May Suggest Future Drug Targets” June 23, 2009.