In a few weeks, the American Psychiatric Association will release its new edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). This volume will tweak several current diagnostic categories, from autism spectrum disorders to mood disorders. While many of these changes have been contentious, the final product involves mostly modest alterations of the previous edition, based on new insights emerging from research since 1990 when DSM-IV was published. Sometimes this research recommended new categories (e.g., mood dysregulation disorder) or that previous categories could be dropped (e.g., Asperger’s syndrome).
The goal of this new manual, as with all previous editions, is to provide a common language for describing psychopathology. While DSM has been described as a “Bible” for the field, it is, at best, a dictionary, creating a set of labels and defining each. The strength of each of the editions of DSM has been “reliability” – each edition has ensured that clinicians use the same terms in the same ways. The weakness is its lack of validity. Unlike our definitions of ischemic heart disease, lymphoma, or AIDS, the DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure. In the rest of medicine, this would be equivalent to creating diagnostic systems based on the nature of chest pain or the quality of fever. Indeed, symptom-based diagnosis, once common in other areas of medicine, has been largely replaced in the past half century as we have understood that symptoms alone rarely indicate the best choice of treatment.
As a result of the DSM’s shortcomings, Insel says that NIMH will be abandoning this classic manual of psychiatry, in favor of something he calls “Research Domain Criteria.” Under this plan, future psychiatric research will focus on characterizing and treating diseases on the basis of their underlying biology, rather than the DSM’s symptomology.
This drew loud cheers from longtime critics of psychiatry, who are legion. Here at last was a high-profile statement affirming their belief that the field’s “Bible” – and by inference the entire field – is bogus. Many news articles picked up the same angle, but that view vastly overstates what’s actually going on here. In fact, what we’re seeing is just the normal progression of medical science, in a way that should surprise exactly nobody.
Almost every field of medicine has had transitions like this. Two hundred years ago, the germ theory of infectious disease was widely considered absurd. Now we know it is fact, and infectious disease is the most definitive of medical specialties. That doesn’t mean the old knowledge was entirely useless, though; Edward Jenner developed a highly effective vaccine against smallpox without ever understanding its underlying mechanisms.
The DSM catalogues mental disorders the way an early 19th century doctor would’ve catalogued rashes. It’s probably right, and in some cases very right, about a few of them. It’s probably wrong about many more. Psychiatrists I’ve met (and the one I married) generally regard the DSM categories as a necessary evil, not a definitive reference. The “Bible” moniker is a straw man. Nobody likes the DSM, but it serves a purpose and has no obvious alternatives.
And that’s the rub. The NIMH’s brief is research, so they can reject or adopt whatever categories they like for their studies. Nobody shows up there for routine treatment of schizophrenia, or major depression, or bipolar disorder. NIMH should be using the latest neuroscience. The latest neuroscience, though, can’t tell us much about the vast majority of mental disorders, and some of the things it can tell us may turn out to be wrong. We might someday have a blood test for depression, or we might not. We can say with certainty that we don’t have one right now.
Insel’s alternative framework is nowhere near ready for prime time. Until it is, what should we do about the guy who’s running out into traffic to tell people he’s the Messiah, or the woman who is in perfect physical health, but catatonic, or the elementary-age child who can only communicate in screams?
It’s telling that some of the people calling for the death of the DSM-5 are remarkably reticent when it comes to offering alternatives. Perhaps that’s because the more you ponder the problem the trickier it gets. Tell patients with no medical training that the field’s diagnoses are largely theoretical and expect them to appreciate the nuances? Let all of the world’s con-men sell them snake oil? Tell them to come back in a few decades? Or use a deeply flawed framework that at least has a chance of being partly correct?