The first direct evidence that attention deficit hyperactivity disorder (ADHD) is a genetic condition has been unveiled by a team from Cardiff University. The research, published in the medical journal The Lancet, suggests that children with ADHD were more likely to have small segments of their DNA duplicated or missing than other children.
The study also found significant overlap between these segments, known as copy number variants (CNVs), and genetic variants implicated in autism and schizophrenia. The team claim that this provides strong evidence that ADHD is a neurodevelopmental disorder. In simple terms, this means that the brains of children with ADHD differ from those of other children.
“We hope that these findings will help overcome the stigma associated with ADHD,” says Professor Anita Thapar, who led the research. “Too often, people dismiss ADHD as being down to bad parenting or poor diet. As a clinician, it was clear to me that this was unlikely to be the case. 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.”
Roughly two per cent of children in the UK are thought to have ADHD, which typically makes them excessively restless, distractible and impulsive. These problems often lead to significant difficulties at school and in the home and can manifest themselves in problem or challenging behaviour. The condition is often treated by a combination of behavioural therapy and medication, which can result in a reduction in symptoms
The research team at Cardiff University analysed the genomes of 366 children, all of whom had been given a clinical diagnosis of ADHD, against over 1,000 control samples. “ADHD is not caused by a single genetic change, but is likely caused by a number of genetic changes, including CNVs, interacting with a child’s environment,” says Dr Kate Langley, a member of the research team.