Ryan was eight when he tried to kill himself. He saved up his Ritalin tablets until there seemed to be enough for an overdose, then knocked them back and waited to die. Later, after he had been very sick, his mum asked why he had done it. “Because I’m too naughty,” he said. “I’m just a nuisance to everyone.”

Ryan is constantly in trouble at school and at home. He has been diagnosed with ADHD (attention deficit hyperactivity disorder), a “developmental disorder” involving problems with concentration and self-control. ADHD did not exist as a medical condition until 40 years ago but is now thought to affect about 5% of the population. The vast majority of sufferers are male.