Children suffering from attention deficit hyperactivity disorder (ADHD) are not disrupting their school classes or their neighborhoods because of poor parenting, UK scientists said on Wednesday.

Rather they are a product of a genetic malfunction made worse by anarchic surroundings, they believe.

“ADHD is not a product of bad parenting,” David Daley from the University of Wales told reporters. “You need a genetic predisposition and a chaotic environment to express the symptoms.”

He said studies had found that parents of ADHD children who themselves suffered from the disease actually had a better relationship with their offspring than normal parents of an ADHD child.

Professor Eric Taylor of Britain’s Institute of Psychiatry said ADHD in its mildest form affected up to five percent of children worldwide but was either over- or under-recognized depending on the country.

In Britain it was generally overlooked while in the United States it was hugely over-diagnosed and over-medicated, he said.

In its most acute form it is known as hyperkinesis - with sufferers being inattentive, overactive and impulsive.

“At its most severe it is a hidden disease,” Taylor said. “If left untreated, it leads to a four-fold rise in mental disorders in adulthood.”

“Families need acceptance and understanding. It should be thought of as a long-term subtle disability.”

It was not caused by one gene, but a bundle of several which were still only starting to be investigated.

Taylor said studies had shown that there were even observable differences in the brains of ADHD sufferers.

“The areas of the brain involved in self-control are smaller in ADHD sufferers,” he said. “Those not treated are more likely to turn to anti-social behavior or self-abuse.”

Treatment was usually with drugs such as Ritalin or with behavioral intervention.

But the illness was not all bad news, Taylor said. The fact that it was found globally suggested that the genes involved in it might be linked to survival traits in some way.

“Mild levels of hyperactivity can be beneficial. Human society needs its hyperactives,” he said, noting that sufferers tended to have fast reactions but were no good at forward planning.

Speaking at the British Association for the Advancement of Science annual meeting, he noted that comedians Billy Connolly and Robin Williams had both identified themselves as ADHD sufferers.