Attention-deficit hyperactivity disorder is a genetic condition, research has suggested.
The behaviour of children with the disorder can be explained by differences in the brain rather than parenting skills or diet, according to the study by scientists at Cardiff University.
The team found rare copy number variants - where small segments of DNA are duplicated or missing - were twice as common in children with ADHD than those without the condition.
According to the research, published in the Lancet, there was overlap between the affected parts of the DNA and those associated with autism and schizophrenia.
The most significant overlap was found at a particular region on chromosome 16, which has previously been implicated in schizophrenia and other psychiatric disorders and spans a number of genes including one known to play a role in the development of the brain, the team found.
