Parents of children who cannot concentrate, are prone to fidget and act impulsively may for the first time be able to escape criticism of their child-rearing skills, after scientists announced that attention deficit hyperactivity disorder (ADHD) is a genetic condition.
One in 50 children are affected by the disorder, which attracts disapproving looks and frequent scolding from people convinced that the bad behaviour is due to poor parenting, too much sugar or too many additives in the child's diet.
Children with ADHD are impulsive and have an inability to focus, which causes difficulties at home and school, placing immense strain on their families. The burden has been aggravated by the stigma attached to the disorder which attributes responsibility to the parents.
Now scientists from Cardiff University say the origin of the behaviour is in the genes. They compared the DNA of two groups of children with and without ADHD and have discovered differences between them which provide the first direct evidence of a genetic cause.
Anita Thapar, professor of child and adolescent psychiatry at Cardiff University, said: "We are really excited by these findings. We have known ADHD runs in families but this is the first evidence of a direct genetic link. We hope these findings will help overcome the stigma associated with ADHD.
"Too often people dismiss it as being down to bad parenting or poor diet. As a clinician it was clear to me 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 the brains of other children."
ADHD is known to run in families – identical twins have a three-in-four chance of having the condition if their twin also has it. But, until now, debate has raged over whether the "heritability" of the condition was the result of a shared environment or shared genes.
The researchers analysed the genomes of 366 children who had been diagnosed by doctors with ADHD and compared them with the genomes of 1,000 controls. They found that chunks of DNA which were either missing or duplicated were twice as common in the children with ADHD. The findings are published in The Lancet.
Professor Thapar said the parts of the genome affected were the same as those involved in autism and schizophrenia, suggesting a potential overlap between the conditions.
"It gives us a window into the biology of the brain. The findings will help unravel the biological basis of the condition and could help develop treatments."
Treatment for ADHD is limited to alleviating the symptoms with drugs, behavioural management and school support. "It is palliative. It doesn't cure but it takes the edge off the symptoms. The hope is that by better understanding the biology we can have more specific types of medication," Professor Thapar said.
She added that there was no evidence that bad parenting or poor diet caused ADHD, although it could affect behaviour in other children. "We have looked – but we have found none. To manage children with ADHD you need to be a super-parent to handle the difficulties. But that doesn't mean the parenting caused the difficulties," she said.
Case study: 'Shopping with the children is a trial'
ADHD runs in the Challen family. Stephen, 36, was diagnosed as a child. Now his 10-year-old daughter Stephanie has been diagnosed and his other three children Andrea, 13, Shania, five, and Luke, one, are also being investigated.
Stephen was a wanderer as a child, frequently getting lost, and struggled at school. From her earliest years he noticed Stephanie had difficulty concentrating and had crying tantrums.
"Most children you can put in front of the TV but she would tolerate only 30 seconds."
Going out became a trial. "It's the looks you get. If we took the kids shopping it would be horrendous. People treat Stephanie as if she was less than intelligent when she is very intelligent. It affected her confidence. So we avoid it."
Stephen is an IT technician in Southend, Essex. His wife Madeline, 36, looks after the family. "Madeline has struggled to keep the children behaving within acceptable bounds. The children can't control their behaviour and smacking them won't have the effect. They need to learn the capability to avoid the behaviour. We need to get people away from the idea this is caused by bad parenting."