Study links attention deficit to missing, repeated DNA

LONDON — Don't blame attention-deficit hyperactivity disorder on poor parenting or excess candy. A new study suggests it's all about genes.

Hyperactive children have a larger proportion of small DNA segments that are either duplicated or missing, according to a study published online today by the medical journal the Lancet.

The findings may help remove the stigma attached to the disorder, said Anita Thapar of Cardiff University School of Genetics, the study's lead author.

Thapar and her colleagues compared 366 children, ages 5 to 17, who had been diagnosed with ADHD with 1,047 who hadn't. Children with other diagnosed psychiatric illnesses weren't included in the study. Kids with ADHD were almost twice as likely to have stretches of large, rare, chromosomal deletions and duplications know as copy number variants, the researchers found.

The genetic abnormalities were found in the same positions as in patients with other neuro-developmental disorders like autism and schizophrenia, suggesting a common biological basis for the diseases, the researchers said.