Diagnostic complexity and depression: time to allow for uncertainty

The last 25 years have seen the evolution of an increasingly ordered and structured approach to psychiatric diagnosis, recognized by some (e.g. Andreason, 1995) as dating from publication of the work of Eli Robins and colleagues in St. Louis (e.g. Robins & Guze, 1970). Their call for a more systematic scientific method to be applied to the diagnostic process, through the development of explicit criteria, has been heeded and has provided the foundation to many of the advances in psychiatry that have been subsequently achieved. This objective has been satisfied at intervals by the publication of modified criteria intended to be ever more precisely crafted and to embody consensus views on the formal requirements to meet diagnostic states. In tandem with these changes in criteria, has been the linked development of diagnostic instruments, each designed to represent the diagnostic rules specified within individual or competing schemes. Inevitably, while many regard this period during which diagnostic rules have become more formally expressed as a necessary scientific step for psychiatry, others (e.g. Snaith, 1987; Blacker & Tsuang, 1992; Van Praag, 1993; Charlton, 1995) have expressed their concerns over aspects of the resulting classifications; for example, Charlton has recently argued for the complete abandonment of the major syndromal categories in favour of a nosology informed through a new discipline of cognitive neuropsychiatry. These current criticisms of the outcome of diagnostic rule development represent the contemporary face of what has been a continuing concern with aspects of this work over the last 25 years. They have naturally arisen from the formal steps needed to develop and refine diagnostic procedures (concerning, for example, their consensus, comprehensiveness, the standardization of items, together with reliability, validity and cross-cultural considerations), the increasing recognition of the importance of taking the 'longitudinal view' for informing opinions on psychiatric status and from the development of'expert systems' designed to enhance diagnostic accuracy. The papers published by Kendell during the early part of this period serve as a reminder of some of the central and continuing issues (e.g. Kendell, 1976, 1982; Kendell & Brockington, 1980). His concerns were with the developing complexity of the classificatory schemes, the need to establish a consensus on how the depressions (in particular) should be classified and, given the existence of rival definitions, the need to employ multiple classificatory schemes simultaneously for research purposes. Jablensky et al. (1983) and Jablensky (1987) have set out similar views to those of Kendell, also formulating a critique of aspects of the competing diagnostic systems that were perceived, in particular, as having only limited value for the prognostic evaluation of the affective disorders. The opinion again being expressed was that the problems identified by Kendell had not been resolved but had probably been exacerbated; evidence being marshalled to show that the different operational criteria embodied in the various schemes had low concordance. A further issue raised by Kendell, concerned what he called the 'boundary problem', meaning by this the apparent absence of points of discontinuity or rarity between psychiatric syndromes and their appearance of merging into one another in a seamless fashion. The possibility being considered was that if syndromal neighbours could be mapped out, then this would improve the likelihood of specifying their potentially different aetiologies and perhaps responsivity to treatment. The continuing evolution of diagnostic schemes has depended, in part at least, upon attempts to specify more