Sub-typing depression, I. Is psychomotor disturbance necessary and sufficient to the definition of melancholia?

Melancholia is most commonly distinguished from non-melancholic depression by the presence of psychomotor disturbance (PMD) and a set of 'endogeneity' symptoms. We examine the capacity of an operationalized clinician-rated measure of PMD (the CORE system) to predict diagnostic assignment to 'melancholic/endogenous' classes by the DSM-III-R and Newcastle systems. Examining a pre-established CORE cut-off score (> or = 8) against independent diagnostic assignment, PMD was present in 51% of those assigned as melancholic by DSM-III-R, and 85% of those assigned as endogenous by the Newcastle system, quantifying the extent to which it is 'necessary' to the two definitions of 'melancholia'. Additionally, multivariate analyses established that the addition of a refined set of historically suggested endogeneity symptoms added only slightly to overall discrimination of melancholic and non-melancholic depressives. While only few endogeneity symptoms independent of psychomotor disturbance were suggested, their specific relevance varied against system definition of melancholia (appetite/weight loss and terminal insomnia being identified for DSM-III-R; anhedonia for Newcastle; and diurnal variation in mood and energy for both systems). Results allow consideration of the relative importance of two domains (psychomotor disturbance and 'endogeneity' symptoms) to clinical definition of melancholia, and have the potential to assist both classification and pursuit of neurobiological determinants. We interpret findings as suggesting a 'core and mantle' model for conceptualizing the clinical features of melancholia, with psychomotor disturbance as the core and with independent endogeneity symptoms as only a thin mantle.