Cardiff University researchers and their colleagues found that people with attention-deficit hyperactivity disorder have an increased load of copy number variants. In The Lancet, they describe their genome-wide analysis 410 children with ADHD and 1,156 unrelated matched controls from Britain, an analysis that they repeated with Icelandic patients and controls. They point out that people with ADHD had "an excess of chromosome 16p13.11 duplications" and say that their findings indicate that "ADHD is not purely a social construct." Senior author Anita Thapar tells the Associated Press that "this is the first time we've found that children with ADHD have chunks of DNA that are either duplicated or missing."