Nature of pathology: The character of danger implicit in functional impairment

Objective: To facilitate clinical and scientific consensus in definitions of psychiatric disorders and with regard to the nature and meaning of pathology more generally. Method: An essay based on a review of definitional problems encountered by psychiatric epidemiologists, with examples taken from selected studies of historic importance. A remedy is suggested and illustrated by experiences with its use in the Stirling County Study. Results: A concept of pathology, termed for reference as 'impairment- risk,' is defined as the danger that functional impairment carries for subsequent health adversities. The concept is based on the classical notions of Rudolf Virchow, the empirical orientations of Adolf Meyer's psychobiology, the functional concepts of physiology, and the dynamics implied by evolutionary biology. The ideas embedded in 'impairment-risk' are beginning to be represented in official classifications of mental disorders. Conclusions: Impairment-risk has potential in the further development of psychiatric epidemiology because of the connections made possible among neuroscience, genetics, general medicine, psychology, and the more empirical of the social and behavioural sciences.