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(CBS) a new gene study may provide answers for what causes attention-deficit/hyperactivity disorder (ADHD), one of the most common behavior disorders among kids.

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Scientists say they’ve identified variations in four genes involved in so-called “brain signaling pathways,” and those variations may unlock clues on how to treat the disorder.

For the study – published in the Dec. 4 issue of Nature Genetics – scientists at the Children’s Hospital of Philadelphia analyzed the whole genomes of 1,000 kids with ADHD, compared with those of 4,100 kids without ADHD. The scientists looked for differences in the number of deletions or duplications of DNA.

What did they find? Kids with ADHD had a significant number of differences on four particular genes involved in a pathway that’s thought to relay information between the neurons and the brain.

“At least 10 percent of the ADHD patients in our sample have these particular genetic variants,” study author Dr. Hakon Hakonarson, director of the Center for Applied Genomics at The Children’s Hospital of Philadelphia, said in a written statement. “The genes involved affect neurotransmitter systems in the brain that have been implicated in ADHD, and we now have a genetic explanation for this link.”

Overall, 5.2 million U.S. children ages 3 to 17 have been diagnosed with ADHD, according to the CDC. Thousands of other genes may contribute to ADHD risk, but the scientists said that identifying a gene responsible for 10 percent of cases is a “robust” finding that can help others.

How? Scientists say new drugs could target these pathways and provide a more effective treatment for ADHD.

“This research will allow new therapies to be developed that are tailored to treating underlying causes of ADHD,” study co-author Dr. Josephine Elia, a child psychiatrist and ADHD expert at Children’s Hospital, said in the statement. “This is another step toward individualizing treatment to a child’s genetic profile.”

WebMD has more on ADHD.