The descriptive epidemiology of internalizing and externalizing psychiatric dimensions.

Background: There is a growing recognition that comorbidity among individual mental disorders is best explained by the broad, psychiatric dimensions of internalization (sub-divided into distress and fear) and externalization. The aims of the current study were to examine the descriptive epidemiology of these psychiatric dimensions.

Methods: Continuous measures of distress, fear and externalization dimensions were obtained from principal components analysis of 11 common ICD-10 mental disorders in a large (N = 10,641) community sample. The relationships between these three dimensions and sociodemographic, physical illness and personality disorder characteristics were determined using multivariate linear regression analyses.

Results: The results suggest that the distress dimension is more strongly related to disadvantageous sociodemographic characteristics and physical health conditions than either the fear or externalizing dimensions. The results also demonstrate some specificity in profiles particularly with regard to the personality disorders.

Conclusions: Greater emphasis should be placed on continuous psychiatric dimensions that are thought to underlie the expression of putatively independent mental disorders.