ICD-11 and operationalism

To the Editor

I commend Bernard J Carroll for his excellent comment on the development of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III) and its followers (Carroll, 2014). I would like to add a remark about his fourth recommendation to the authors of the International Classification of Diseases, 11th Revision (ICD-11): ‘Maintain a clear distinction between making a diagnosis and defining a disorder. This speaks to a fundamental category error that appeared soon after DSM-III and that still persists in the form of checklist menu diagnoses – ironically mostly in research settings. DSM-5 did not fix that.’ Actually, I do not think that there is any ‘error’ from Spitzer and the Washington University group here. Rather, it was a deliberate, epistemological decision to build DSM-III on the principles of logical empiricism and therefore to give operational definitions of psychiatric diagnoses (Schwartz and Wiggins, 1986). Operationalism implies that there is no difference between the definition of a concept and the method to assert whether the concept applies in a specific circumstance. For instance, an operational definition of body temperature would run along the following lines: take a thermometer (specified in some way), put it in the rectum of the involved body, wait for 5 minutes, take it out, read it. This is both the measurement operation and the operational definition of the concept: defining the concept and measuring it are the same thing in an operationalist approach. Of course, such a definition of temperature is very superficial to most scientists. The psychologist bemoans the lack of any link to the psychological context; the infectiologist wonders where have the interleukins gone; the neurologist looks in vain for a mention of the role of the hypothalamus; the physicist is baffled that the definition says nothing of the kinetic energy dissipating in heat; and so on, and so forth. This is the nosology that psychiatry has been left with: operational, shallow, and perhaps very unscientific in its reluctance to rely on the complex science of psychopathology. What is a depression? ‘Ask the patient if he’s been sad over the past 2 weeks, ask the patient if he’s been tired over the past 2 weeks (…), count how many yeses you have, if more than n, this is a depression.’