The first direct evidence of a genetic link to attention-deficit hyperactivity disorder has been found, a study says.
Scientists from Cardiff University, writing in The Lancet, said the disorder was a brain problem like autism - not due to bad parenting.
They analysed stretches of DNA from 366 children who had been diagnosed with the disorder.
But one clinical psychologist argued that what happened in children's early years was more crucial than genetics.
At least 2% of children in the UK are thought to have attention-deficit hyperactivity disorder (ADHD).