LONDON — Children with attention deficit hyperactivity disorder are twice as likely to have missing or extra chromosomes than normal children — the first evidence that the disorder is genetic, a new study says.
British researchers compared the genomes of 366 white British children from 5 to 17 years old with attention deficit hyperactivity, or ADHD, to those of more than 1,000 similar children without the disorder. The scientists focused on a sequence of genes linked to brain development that has previously been connected to conditions such as autism and schizophrenia.
In children without ADHD, about 7 percent of them had deleted or doubled chromosomes in the analyzed gene sequence. But among children with the disorder, researchers discovered about 14 percent had such genetic alterations.
“This is the first time we’ve found that children with ADHD have chunks of DNA that are either duplicated or missing,” said Anita Thapar, a professor at the MRC Centre in Neuropsychiatric Genetics and Genomics at Cardiff University who was one of the study’s authors.
She said the findings are too early to affect diagnosis or treatment and are applicable only to people of European Caucasian descent because studies have not been done yet on other ethnicities.
The condition is estimated to affect millions of children around the world, and scientists have long thought the disorder is genetic.
U.S. experts estimate ADHD affects from 3 percent to 5 percent of school-age U.S. children.
