June 25 (HealthDay News) -- Hundreds of gene variations that may be associated with attention-deficit/hyperactivity disorder (ADHD) have been identified by U.S. researchers.
Many of these genes were known to be involved in learning, behavior, brain function and neurodevelopment, but this is the first study to link them to ADHD. The findings appear in the June 23 online edition of Molecular Psychiatry.
"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," study author Dr. Josephine Elia, a psychiatrist and ADHD expert at The Children's Hospital of Philadelphia, said in a school news release.
For this study, Elia and her colleagues analyzed genomes from 335 ADHD patients and their families, and compared them to more than 2,000 children without ADHD. The hundreds of gene variations were found to occur more often in children with ADHD than in normal children.
"When we began this study in 2003, we expected to find a handful of genes that predispose a child to ADHD," study co-leader Peter S. White, a molecular geneticist and director of the Center for Biomedical Informatics at The Children's Hospital, said in the release.
"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," White said.
The cause of ADHD isn't known, but studies have shown that it's strongly influenced by genetics.
ADHD, which affects about one in 20 children worldwide, may include symptoms such as hyperactive behavior, impulsivity, inattention, impaired planning and organizing skills, and difficulty maintaining focus.
SOURCE: The Children's Hospital of Philadelphia, news release, June 23, 2009