Scientists have found the first direct evidence that attention deficit/hyperactivity disorder is a genetic disorder after finding that kids with ADHD are twice as likely to have missing or extra chromosomes than normal children.
British researchers compared the genomes of 366 British children between the ages of five to 17 years old with ADHD, to those of more than 1,000 similar children without the disorder. They focused on a sequence of genes linked to brain development that has previously been connected to conditions like autism and schizophrenia.
They found that in kids without ADHD, seven per cent had deleted or doubled chromosomes in the analyzed gene sequence. But among children with the disorder, researchers discovered about 14 per cent had such genetic alterations.
Scientists also found that 36 per cent of children with learning disabilities in the study had the chromosomal abnormalities, compared to those with a normal IQ.
The findings should help dispel myths that ADHD is caused by bad parenting or too much TV, although a child's environment may also play a told.
"This is really exciting because it gives us the first direct genetic link to ADHD," Anita Thapar, a Cardiff University psychiatry professor, who led the study, told reporters at a briefing about the findings.
"Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children," she said.
The findings so far are applicable only to people of European Caucasian descent because studies have not been done yet on other ethnicities. But with further research, the findings could lead to treatments.
Thapar said the findings would help unravel ADHD's biological basis, "and that's going to be really important in the future to develop new and much more effective treatments."
ADHD is estimated to affect around three to five per cent of children globally. It is seen far more often in boys than in girls.
Children with ADHD are excessively restless, impulsive and easily distracted, and often experience difficulties at home and in school. There is no cure, but the symptoms can be controlled by a combination of medication and behavioral therapy.
