Special Feature: Extent of Comorbidity Between Mental State and Personality Disorders

Comorbidity between major psychiatric disorders (Axis I) and personality disorders (Axis II) is widespread, often extremely strong, and invariably confusing. The strongest associations are found between substance use and the cluster B (flamboyant) personality disorders, anxiety disorders and the anxious/fearful personality group (cluster C), and between somatisation and both cluster B and C disorders. The significance of these associations is far from clear, and almost certainly include more than one type of relationship. Empirical studies of patients with and without Axis I and II comorbidity show that the presence of a personality disorder can affect the outcome of treatment, both positively and negatively, in a way that currently appears unpredictable. One useful way of interpreting this comorbidity is by postulating personality dispositions that make some people prone to certain mental state disorders.