OLD DATA, NEW INTERPRETATION - A REANALYSIS OF LEWIS,AUBREY THESIS

Sir Aubrey Lewis studied 61 depressives in considerable detail, princi pally cross-sectionally but also by reviewing progress. He concluded t hat he could find no qualitative distinctions between the depressed pa tients and thus established himself as a strong and influential advoca te of the unitary view of depression (i.e. that depression varies dime nsionally, not categorically). Subsequently, Kiloh & Garside (proponen ts of the binary view of two depressive 'types') coded the Lewis data and undertook a principal components analysis. They claimed success in distinguishing 'endogenous' and 'neurotic' depressive types within Le wis' sample. In this paper we re-analyse the data set using both a lat ent class categorical approach and mixture analyses. We suggest that a ny demonstration of sub-types was limited by relative homogeneity of t he sample (in that up to 80 % had probable or possible psychotic condi tions), and by Lewis rating a number of important features (e.g. delus ions) dimensionally rather than categorically. Nevertheless, we identi fy one categorical class (essentially an agitated psychotic depressive condition) and a residual (presumably heterogeneous) class. The prese nce of those two classes was supported by demonstrating bimodality in composite scores derived from the fourteen differentiating clinical fe atures (and not evident when all clinical features were considered), a nd formally confirmed by mixture analyses. Membership of the categoric al class was determined principally by psychotic features (delusions a nd hallucinations) and by objectively-judged psychomotor disturbance, and we consider the nature of that 'class'. Lewis' data set is unusual (in having self-report and observationally rated data), and historica lly important in demonstrating that conclusions may depend on the choi ce of variables examined and analytical approaches.