Validity of nosological classification

Since their official introduction, the International Classification of Diseases, 10th Revision (ICD-10),1 and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV),2 operational classification systems have largely become an integral part of the body of knowledge of psychiatrists throughout the world and instruments they constantly refer to. In this article I look at some of the questions that have been raised in connection with these classifications, both as a result of the growing number of critical analyses and of my own experience. This short contribution does not claim to provide exhaustive answers, but merely to stimulate further discussion. Psychiatrists probably all started adopting operational diagnostic classification systems, such as the ICD and DSM classifications, on the assumption that the reliability of the diagnoses therein defined was unequivocally demonstrated to be very high across the centers and even countries of evaluation, without realizing that the general consensus was based on the lowest level of validity conceivable, since it resulted from the mutual agreement of experts rather than on any proven facts concerning the etiology of mental disorders. This means that in the absence of biological markers for most psychopathological disorders, diagnostic features were based on clinical descriptions, resulting in “official” nosological groupings. One of the main objections raised by clinical psychiatrists was that in many instances diagnoses were based on the numbers of certain symptoms.3 Nevertheless, in spite of initial warnings of oversimplification, the two most widely used official classifications - DSM and ICD - came to be largely regarded as nosologically valid by medical doctors, official institutions, and even the public at large. The interesting, but logical, paradox is that those least satisfied with these so universally acclaimed classifications are probably the psychiatrists. In this article, I would like to briefly discuss two frequently asked questions: (i) what is the validity of the current diagnostic process? and (ii) what are the weak points of the DSM and ICD classifications?