Multiple Axis-II Diagnoses of Personality Disorder

Abstract

Background Simultaneous diagnosis of more than one personality disorder (PD) has been termed ‘comorbidity’ or ‘co-occurrence’ implying that single diagnoses are the norm and multiple diagnoses interesting exceptions. Surveys of PD subjects in fact show 1.5–5.6 diagnoses per subject. Our study explores the hypothesis that multiple PD diagnosis is common and increases with increasingly personality disordered populations. Method The PDQ–R questionnaire was administered to three UK samples: referrals for specialist PD in-patient treatment (n = 275); high tariff offenders attending a probation centre (n = 57); and undergraduate students (n = 274). Results Means of 6.0 (95% CI 5.7–6.3), 4.0 (3. 1–5.0) and 3.4 (3.0–3.8) PDQ–R diagnoses per subject were found respectively. High rates of PD diagnosis in individual subjects suggest that multiple diagnosis is the norm rather than the exception. Conclusions Multiple diagnosis of PD is better construed as ‘breadth’ of psychopathology rather than comorbidity and is a function of sampling frame. High rates of multiple diagnoses question the interpretation of studies of any single PD. The graded construct of ‘breadth’ of axis–II pathology may further our understanding of PD.