Beyond categorical diagnostics in psychiatry: Scientific and medicolegal implications

Conforming to a medical disease model rooted in phenomenology and natural science, psychiatry classifies mental disorders according to signs and symptoms considered to be stable and homogeneous across individuals. Scientific studies addressing the validity of this classification are scarce. Following a seminal paper by Robins and Guze in 1970, validity of categories has been sought in specific criteria referring to symptoms and prognosis, aggregation in families, and "markers", preferentially laboratory tests. There is, however, a growing misfit between the model and empirical findings from studies putting it to the test. Diagnostic categories have not been shown to represent natural groups delineated from the normal variation or from each other. Aetiological factors (genetic and/or environmental), laboratory aberrations, and treatment effects do not respect categorical boundaries. A more adequate description of mental problems may be achieved by: 1) a clear definition of the epistemological frame in which psychiatry operates, 2) a basic rating of the severity of intra- and interpersonal dysfunctions, and 3) empirical comparisons to complementary rather than exclusive dimensions of inter-individual differences in context-specific mental functions, treatment effects, and laboratory findings. Such a pluralistic understanding of mental health problems would fit empirical models in the neurosciences and postmodern notions of subjectivity alike. It would also clarify the assessment of dysfunction and background factors in relation to the requisites for penal law exemptions or insurance policies and make them empirically testable rather than dependent on expert opinion on issues such as whether a specific dysfunction is "psychiatric", "medical", or ascribable to "personality". (C) 2009 Elsevier Ltd. All rights reserved.