With three years still left until publication, the fights over the new version of the psychiatric diagnostic manual, the DSM-V, are hotting up and The New York Times has a concise article that covers most of the main point of contention.

- “What you have in the end,” Mr. Shorter said, “is this process of sorting the deck of symptoms into syndromes, and the outcome all depends on how the cards fall.”

- Psychiatrists involved in preparing the new manual contend that it is too early to say for sure which cards will be added and which dropped.

Although I doubt the DSM committee are using that exact metaphor, it certainly illustrates the point that the process requires a certain degree of value-judgement.

It’s interesting, however, that the public debate is currently focused on whether certain diagnoses should be included or not, rather than whether diagnosis itself is useful for psychiatry.

We’ve had psychometrics for a good 100 years that allow us to measure dimensions of human experience and performance with a much greater degree of accuracy than clinical diagnosis allows.

The slightly obsessive need to classify everything is both an inheritance from the infection model of disease, where one either has the pathogen or does not, and is encouraged by the US health care system, where insurance companies will only pay for treatment if it is diagnosed with an ‘official’ diagnosis.

Nevertheless, it is perfectly possible to treat someone based on continuous measures of distress, impairment and functioning using evidence-based cut-off points to judge whether a particular treatment should be applied.

In fact, many physical diseases are treated in exactly this way. The definitions of obesity, hypertension, diabetes and many others rely on an evidence-based cut-off point on a continuous scale of weight, blood pressure and blood glucose level.

There is no qualitatively different cut-and-dry distinction between just below the cut-off and just above it – it’s just the point at which outcome studies predict that other things get much worse.

So rather than questioning the process, we need also to question the system, because diagnoses are tools and we need to know when and where they are most useful.

Link to NYT ‘Psychiatrists Revise the Book of Human Troubles’.

– Dr. Vaughan Bell, main blogger at Mind Hacks, is a clinical and research psychologist interested in understanding brain injury, mental distress and psychological impairment. He is currently at the Departmento de Psiquiatria in the Universidad de Antioquia and the Hospital Universitario San Vicente de Paul, in Medellin, Colombia, where he’s a visiting professor. He’s also a visiting research fellow at the Department of Clinical Neuroscience at the Institute of Psychiatry, King’s College London.