Prevalence of personality disorder in alcohol and drug services and associated comorbidity

Aims To compare the prevalence of personality disorder in alcohol and drug populations with special attention to its impact on psychopathology and service characteristics. Design Cross-sectional survey. Setting Three alcohol and four drug services in four urban UK centres. Participants Two hundred and sixteen drug and 64 alcohol service patients randomly sampled from current treatment populations. Measurements A treatment population census recorded demographic and diagnostic data. Patient interviews assessed the presence cluster type and, severity of personality disorder using the Quick Personality Assessment Schedule (PAS-Q). Other psychopathology was measured using the Comprehensive Psychopathological Rating Scale (CPRS). A case-note audit recorded psychotic psychopathology using the OPCRIT schedule and data regarding social morbidity. Findings The overall prevalence of personality disorder was 37% in the drug service sample and 53% in the alcohol service sample. The distribution of severity and clusters differed markedly between the two samples. There was a significant association between the severity of personality disorder and psychopathology in both samples. Levels of morbidity associated with clusters B and C were similar. Clinical diagnosis of personality disorder showed high specificity but low sensitivity when compared to PAS-Q. Conclusions In both alcohol and drug service populations, personality disorder is associated with significantly increased rates of psychopathology and social morbidity that worsens with increasing severity of the disorder. Despite this, personality disorder is poorly identified by clinical staff. The PAS-Q may be useful as a clinical assessment tool in the substance misuse population for the early identification and management of patients with personality disorder.