Dr Godfrey Pearlson on the Merits of Using Biological Measures to Classify Psychiatric Diseases

Current diagnostic tools, such as the Diagnostic and Statistical Manual of Mental Disorders (DSM), rely on symptoms to diagnose psychiatric diseases, but using biological measures instead could provide a more reliable, valid method of classifying these syndromes, said Godfrey Pearlson, MD, professor of psychiatry and neuroscience, Yale School of Medicine.


What are the advantages of using biologic measures to classify disease instead of the clinical DSM diagnoses?

Clinical DSM diagnoses are based on phenomenology, that is, what we observe in terms of patients’ symptoms and their clinical course. That’s basically where the rest of medicine was in the 17th and 18th century, before we could identify actual diseases where we knew their underlying cause, their etiology. If you rely only on symptoms, then you have something that’s akin to having fevers or dropsy or cough, where you have just a loose syndrome that everyone can agree on reliably but there’s no underlying validity. So if you just have people who are coughing up blood in medicine, then they could have pneumonia or lung cancer or severe asthma or a really bad cold, and there’s no way to sort them out without underlying biological measures.

So that’s pretty much where we are, I think, in psychiatry at the moment. Biology’s a reliable, valid method for potentially reclassifying these loose syndromes, figuring out what’s under the hood as far as biology, and that once we understand the origin of the illness and what’s wrong with the person biologically at a brain level, then we can move closer towards finding treatments that are individualized.

What are the consequences of the overlap in the current conditions encompassing psychosis in current diagnostic tools like the DSM?

Basically that we’re sort of groping around in the dark when it comes to defining illnesses. As I tried to suggest, it’s where medicine was in the 18th century before we understood what caused diseases. So before we had stethoscopes or otoscopes to look in people’s ears, we really couldn’t see what was going on and try and take measurements, even a basic measurement like temperature. Once you have reliable biological tools, it gives you an insight into what’s going on. Symptoms alone don’t really do that, cause symptoms overlap horribly all the way through medicine.
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