Category Archives: Dimensional

Thoughts on Kendell’s The Role of Diagnosis in Psychiatry

Robert Kendell (1935-2002) (not to be confused with Kandell or Kendler) was a Welsh psychiatrists who explored many fundamental questions about psychiatry. He is perhaps most famous among philosophers for his 2003 article with Jablensky (distinguishing between utility and validity of psychiatric syndromes), indeed, my interest in that article has resulted in me exploring his earlier work.

His 1975 book covers a lot of ground, including reliability, validity, categorical, dimensional and disease entities. It gives a qualified defense of psychiatry, partly reacting to anti-psychiatrists whilst discussing contemporary issues which were then influencing the formulation of DSM III. His basic message might be ‘psychiatry is not as bad as people make out but it could be improved and we have lots of options for going about doing so’. The book is primarily a discussions of those options for the future.

What struck me was just how familiar it read, the problems he identifies and the various solutions he discusses look very recognizable to a modern philosopher of psychiatry. This was especially true in the introduction (that introduction would be a candidate for employment on undergraduate teaching for philosophy of psychiatry). I just felt like modern philosophy of psychiatry had told me little new on these topics which Kendell’s book had not already discussed (granted, discussed in limited detail, being a short book which covers a lot of ground). An exception would be statistical approaches to validity, where modern statistical approaches are more sophisticated than what he addresses. The second exception is that, whilst his discussion of reliability is sophisticated, he uses empirical studies of the 1970s and beforehand to highlight his claims, whereas today we have much more empirical information about how psychiatrists employ diagnosis.

One possible reasons for the lack of progress is that issues over validity, reliability and categorical really were not so controversial once the DSM III framework was adopted. If you want a reliable categorical system which easily lends to testing for disease entities then DSM is pretty good at this. The problem, and why lack of progress is so concerning, is that after about 40 years of testing categorical classifications for disease entities we simply have not found them. Existing DSM classifications have not been validated. If 40 years ago people said ‘lets see if there are disease entities out there’ then I think the DSM and validity project have done a reasonable job of testing this. However, since the answer came up as generally no, we really need develop something new, something outside traditional approaches. Kendell does discuss dimensional systems and alternatives to disease entities but concludes these are usually difficult to put into practice. So either we need work out how to put them into practise or we need some new developments, something beyond disease entity non-disease entity dichotomy, beyond valid invalid dichotomy. The same may be true for categorical vs dimensional, and even the notion of reliability may need challenging.