Abstract
Objective: To review the problems posed for doctors by the failure of existing taxonomies to provide a satisfactory method for deriving diagnoses in cases of physical/psychiatric comorbidity, and of relating diagnoses on multiple axes.
Method: Review of existing taxonomies and key criticisms. The author was guided in selection by his experience as a member of the working parties involved in the creation of the American Psychiatric Association's DSM-IV.
Results: The attempts of the two major taxonomies, the ICD-10 and the American Psychiatric Association's DSM-IV, to address the problem by use of glossaries and multiple axes are described, and found wanting. Novel approaches, including McHugh and Slavey's perspectives of disease, dimensions, behaviour and life story, are described and evaluated. The problem of developing valid and reliable measures of physical/psychiatric comorbidity is addressed, including a discussion of genetic factors, neurobiological variables, target markers and other pathophysiological indicators. Finally, the concept of depression as a systemic illness involving brain, mind and body is raised and the implications of this discussed.
Conclusions: Taxonomies require major revision in order to provide a useful basis for communication and research about one of the most frequent presentations in the community, physical/psychiatric comorbidity.