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The field of mental health will face its greatest upset in years on Saturday with the publication of the long-awaited and deeply-controversial US manual for diagnosing mental disorders.
Early drafts of the book, the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5, have divided medical opinion so firmly that authors of previous editions are among the most prominent critics.
Known informally as the psychiatrists' bible, the $199 tome from the American Psychiatric Association is the guidebook that US doctors will use to diagnose mental disorders. The latest edition is the first major update in 20 years.
World Health Organisation's International Statistical Classification of Diseases (ICD), the US manual has global influence. It defines groups of patients, and introduces new names for disorders.
Those names can spread, and become the norm elsewhere, but more importantly, the categories redefine the populations that are targeted by drugs companies.
Criticisms have come from almost every corner. There are claims of expansionism, with common experiences and behaviours becoming newly medicalised.
Other behaviours get their own labels: overeating becomes binge eating disorder; keeping too much junk, a hoarding disorder; a bit forgetful could be mild neurocognitive disorder.
Nick Craddock, professor of psychiatry at Cardiff University, and director of the National Centre for Mental Health in Wales, said "Some of the stranger aspects of the US manual will have no impact in Britain. DSM-5 was flawed because definitions of disorders were sometimes changed on the basis of too little fresh scientific evidence."
"I don't believe the science has advanced sufficiently in 20 years since DSM-4 to warrant making a new system," he said. "That essentially is just a group of people agreeing on tweaking things and making them appear a little bit different. That to me is not a very helpful stage in the develop of psychiatric diagnosis. This is the wrong time in history to change the diagnostic system."
Changing the definitions of disorders alters who has them. That affects who gets drugs and other support, and who interventions are trialled on. If the criteria for attention Deficit Hyperactivity Disorder (ADHD) are broadened, then more people are likely to be diagnosed with the condition.
The arrival of DSM-5 will mean the end of Asperger's syndrome in the professional eyes of the US psychiatric arena.
Along with some other autism-related conditions, Asperger's will now be consumed by the new category of "autism spectrum disorder".
Debbie Tucker, chair of the Asperger's Syndrome Foundation, said the label can be useful in treating people, but that some did not want to be labelled. "Labels only become unhelpful and sometimes dangerous if used to discriminate. People with Aspergers are vulnerable to this," she said.
Instead, he said the NIHM would lay the foundations for a new classification system, based on brain imaging, genetics, cognitive science and other research.
"We need to begin collecting the genetic, imaging, physiologic, and cognitive data to see how all the data – not just the symptoms – cluster and how these clusters relate to treatment response," he said.