The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5, has divided medical opinion

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.

Though not used in the UK, where doctors turn to the 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. 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. Temper tantrums become disruptive mood dysregulation disorder (DMDD); grief becomes major depressive disorder (MDD), according to Allen Frances, an American psychiatrist who chaired the task force behind the fourth edition of the manual. 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.

David Clark, professor of experimental psychology at Oxford University, said mental health disorders are often hard to divide into clear categories, because too little is known about them, and there can be major overlaps. But the definitions are often valuable. For example, greater distinctions between various types of anxiety have led to more specific and effective treatments, he said.

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. But he said 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 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 mark the end of Asperger's syndrome in the US.

Along with some other autism-related conditions, Asperger's will now be consumed by the new category of "autism spectrum disorder".

Some people diagnosed with Asperger's are unhappy about the coming change. Carol Povey, director of the National Autistic Society's Centre for Autism, said: "The term Asperger Syndrome is a core part of their identity for many people and they understandably feel anxious about moves to remove the term. The changes won't prevent people from continuing to use it to define themselves and nor should it," she said.

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.

Last month, Thomas Insel, director of the National Institute of Mental Health, declared that the organisation would not use DSM-5 definitions to set its research priorities. Writing about DSM-5 on his blog, he said: "The weakness is its lack of validity. Unlike our definitions of ischaemic heart disease, lymphoma, or AIDS, the DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure." 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.