By Kate Kelland
LONDON, Nov 6 (Reuters) - A wider definition of attention deficit hyperactivity disorder (ADHD) is causing inappropriate diagnosis and unnecessary and possibly harmful medical treatment costing up to $500 million in the United States alone, scientists said on Wednesday.
Less restrictive diagnostic criteria have contributed to a steep rise in diagnoses for the behavioural brain condition -particularly among children - the researchers said, and in the use of stimulant drugs to manage it.
The broader definition also "devalues the diagnosis in those with serious problems", said Rae Thomas, a senior researcher at Australia's Bond University who led an analysis of the problem and has published it in the British Medical Journal.
"The broadening of the diagnostic criteria is likely to increase what is already a significant concern about overdiagnosis," he said. "It risks resulting in a diagnosis of ADHD being regarded with scepticism, to the harm of those with severe problems who unquestionably need sensitive, skilled specialist help and support."
People with the ADHD are excessively restless, impulsive and easily distracted, and children with the condition often have trouble in school. It is most often diagnosed in children, mainly boys, but it is also known to persist into adulthood.
There is no cure, but the symptoms can be kept in check by a combination of behavioural therapy and medications such as Ritalin or a newer drug called Vyvanse.
Experts not directly involved in the analysis said its conclusions were interesting but should be viewed with caution.
"I suspect that the reason for increased prescriptions of Ritalin and similar medications for ADHD has to do with better detection of the condition in children and the recognition that 50 percent or more of children with ADHD still have it as an adult," said Barbara Sahakian, a professor of clinical Neuropsychology at the University of Cambridge.
Ilina Singh, an ADHD expert at King's College London, said given the harms of stigma and misunderstanding of the condition "it is important to take care when making generalised claims about the drivers of ADHD diagnosis".
"In many regions, under-diagnosis and under-treatment of ADHD are also a significant concern," she said.
CRITERIA FOR DIAGNOSIS
To be diagnosed with ADHD, patients should meet criteria set out in either the International Classification of Diseases (ICD), or the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM) - the two systems used around the world to classify mental disorders.
But in their BMJ analysis, Thomas's team noted that definitions of ADHD have been broadened in successive editions of DSM, leading to increasing numbers of diagnoses.
In Australia, data show a 73 percent increase for ADHD medication between 2000 and 2011, they found, while prescriptions in Britain increased two-fold for children and adolescents and four-fold in adults between 2003 and 2008.
Prescribing of methylphenidates and amphetamines - two types of drug used to manage ADHD - increased steadily in the United States between 1996 and 2008, they said, with the greatest increase in adolescents aged between 13 and 18 years.
In the Netherlands, prevalence and prescribing rates for children diagnosed with ADHD doubled between 2003 and 2007.
Europeans are generally more resistant than Americans to the idea of medicating children with ADHD, although attitudes vary from place to place. As a result, sales of drugs in Europe are fairly light, with methylphenidate - the generic ingredient in Ritalin - currently the main treatment used.
But Shire, the world's biggest seller of ADHD drugs, is hoping to change that following European approval of its newer amphetamine-based product Vyvanse - called Elvanse in the EU - at the end of last year.
(Reporting by Kate Kelland; editing by Barry Moody)