A wider definition of attention deficit hyperactivity disorder is causing inappropriate diagnosis and unnecessary and possibly harmful medical treatment costing up to US$500 million (HK$3.9 billion) in the United States alone, scientists said.
Less restrictive diagnostic criteria have contributed to a steep rise in diagnoses for the behavioral brain condition - particularly among children - 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.
"This is likely to increase what is already a significant concern about overdiagnosis. It risks resulting in a diagnosis of ADHD being regarded with skepticism, to the harm of those with severe problems who unquestionably need sensitive, skilled specialist help and support," he said.
People with 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 behavioral 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 generalized claims about the drivers of ADHD diagnosis."
To be diagnosed with ADHD, patients should meet criteria set out in either the International Classification of Diseases or the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, or DSM - the two systems used around the world to classify mental disorders.
But Thomas' 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, while prescriptions in Britain doubled for children and adolescents and fourfold in adults between 2003 and 2008.
Prescribing of methylphenidates and amphetamines - two types of drug used to manage ADHD - increased in the United States between 1996 and 2008, with the greatest increase in adolescents.
Europeans are generally more resistant than Americans to the idea of medicating children with ADHD. 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 or Elvanse at the end of last year.