By Ferris Jabr*

Part 2 of a series

In the offices of psychiatrists and psychologists across the country you can find a rather hefty tome called the Diagnostic and Statistical Manual for Mental Disorders (DSM).

The current edition of the DSM, the DSM-IV, is something like a field guide to mental disorders: the book pairs each illness with a checklist of symptoms, just as a naturalists guide describes the distinctive physical features of different birds. These lists of symptoms, known as diagnostic criteria, help psychiatrists choose a disorder that most closely matches what they observe in their patients. Every few decades, the American Psychiatric Association (APA) revises the diagnostic criteria and publishes a brand new version of the DSM. The idea is to make the criteria more accurate, drawing on what psychologists and psychiatrists have learned about mental illness since the manuals last update.

The fat volume on top is still skinny on the science. Courtesy of Ferris Jabr.

In May 2013, the APA plans to publish the fifth and newest edition of the DSM, which it has been preparing for more than 11 years. On its DSM-5 Development website, the APA states that the motivation for the ongoing revisions was an agreement to expand the scientific basis for psychiatric diagnosis and classification. The website further states that over the past two decades, there has been a wealth of new information in neurology, genetics and the behavioral sciences that dramatically expands our understanding of mental illness.

In other words, the APA intended to make the DSM-5 the most scientific edition of its reference guide yet, which would be a real boon for a book that has been routinely lambasted as fiction borne out of convenience, rather than a solid clinical text grounded in research. Now, only one year away from the planned publication of the DSM-5, most psychiatrists have accepted that the APAs initial optimism about informing revisions with cutting edge science is well intentioned, but premature. Most of the proposed revisions to current DSM criteriamany of which are genuine improvementsare based not on insights from genetics and neuroscience, but rather on clinical experience, prevalence studies and plain old common sense. Indeed, many of these changes could have been made years ago. (For more on these changes, see Psychiatrys Bible Gets an Overhaul, by Ferris Jabr, Scientific American Mind, May/June 2012.)

Cutting and Collapsing Categories

Consider, for example, that the DSM-IV organizes schizophrenia into six types, all of which the APA proposes eliminating from the DSM-5. Why? Because these archaic subcategories were never grounded in empirical research in the first place; they were just what sounded good to the DSM authors of yore. In truth, these ostensible types of schizophrenia probably do not exist. Similarly, the APA is nixing three of the 10 current personality disorders, essentially acknowledging that these were never legitimate illnesses in the first place. So many people fit the criteria for more than one personality disorder simultaneously that 10 varieties become superfluous.

Likewise, the DSM-5 collapses four of the five current pervasive developmental disordersincluding autistic disorder and Aspergersinto a single category called autism spectrum disorders, because there is so much overlap in their respective criteria. None of these revisions are founded on recent revelations from genetics and neuroimaging research. Study after study has failed to discover a set of genes or unusual brain structures that reliably identifies major mental disorders. Rather, these are changes that many psychiatrists have been advocating for the past two decades based on their everyday clinical experience, studies of illness prevalence and the sense that some of the current criteria do not make sense. Despite awareness of these flaws, the APA did not get around to updating the DSM until now, the first substantial revision in 30 years.

Originally posted here:
Science Remains a Stranger to Psychiatry's New Bible