Next month brings the long-awaited publication of the updated (fifth) edition of the “Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the symptom “bible” for psychiatrists around the world.
Debate about the revision, which got under way in 2007, has been ongoing and won’t end with next month’s publication. Much has been written about the controversies, particularly about the expected tightening of the criteria for autism and the adding of bereavement as a symptom of major depression.
But, as Nature reporter David Adam points out in a recent article, there’s been a bigger and broader debate overshadowing the revision, one that has received less media attention but that gets to the very essence of how psychiatrists — and the rest of us — think about mental illnesses:
The stark fact is that no one has yet agreed on how best to define and diagnose mental illnesses. DSM-5, like the two preceding editions, will place disorders in discrete categories such as major-depressive disorder, bipolar disorder, schizophrenia and obsessive-compulsive disorder (OCD). These categories, which have guided psychiatry since the early 1980s, are based largely on decades-old theory and subjective symptoms.
The problem is that biologists have been unable to find any genetic or neuroscientific evidence to support the breakdown of complex mental disorders into separate categories. Many psychiatrists, meanwhile, already think outside the category boxes, because they see so many patients whose symptoms do not fit neatly into them. [Dr. David] Kupfer, [a psychiatrist at the University of Pittsburgh and head of the task force overseeing the DSM-5 revision], and others wanted the latest DSM to move away from the category approach and towards one called ‘dimensionality,’ in which mental illnesses overlap. According to this view, the disorders are the product of shared risk factors that lead to abnormalities in intersecting drives such as motivation and reward anticipation, which can be measured (hence ‘dimension’) and used to place people on one of several spectra. But the attempt to introduce this approach foundered, as other psychiatrists and psychologists protested that it was premature.
Thus, the new DSM will continue to silo mental illnesses, says Adam, even as the walls of those silos are being broken down in clinical practice:
As psychiatrists well know, most patients turn up with a mix of symptoms and so are frequently diagnosed with several disorders, or co-morbidities. About one-fifth of people who fulfill criteria for one DSM-IV disorder meet the criteria for at least two more.
These are patients “who have not read the textbook,” says [Dr.] Steve Hyman, who directs the Stanley Center for Psychiatric Research, part of the Broad Institute in Cambridge, Massachusetts. As their symptoms wax and wane over time, they receive different diagnoses, which can be upsetting and give false hope. “The problem is that the DSM has been launched into under-researched waters, and this has been accepted in an unquestioning way,” he says.
Unfortunately, “the ingrained category approach is actually inhibiting scientific research that could refine diagnoses,” notes Adam, “in part because funding agencies have often favored studies that fit the standard diagnostic groups.”
But other factors also encourage the status quo, he adds:
The proposal [to introduce dimensionality to the DSM-5] was also unpopular with patient groups and charities, many of which have fought long and hard to make various distinct mental-health disorders into visible brands. They did not want to see schizophrenia or bipolar disorder labeled as something different. Speaking privately, some psychologists also mutter about the influence of drug companies an their relationship with psychiatrists. Both stand to profit from the existing DSM categories because health-insurance schemes in the United States pay for treatments based on them. They have little incentive to see categories dissolve.
You can read Adam’s article on the Nature website.