Background: The economic impact of personality disorders on UK health services is unknown.
Aims: To test the hypothesis that people with personality disorders have higher mean health and non-health costs compared with those without personality disorders.
Method: Prospective cohort study design. A total of 303 general practice attenders were followed-up I year after they had been assessed for the presence of personality disorders. Costs were estimated in pound sterling at 1999 price levels.
Results: The mean total cost for patients with personality disorders was pound sterling 3094 (s.d.=5324) compared with pound sterling 1633 (s.d.=3779) for those without personality disorders. Personality disorders were not independently associated with increased costs. Multivariate analyses identified the presence of a significant interaction between personality disorders and common mental disorders and increased total costs (coefficient=499, 95% CI 180.1-626.2, P=0.002).
Conclusions: Personality disorders are not independently associated with increased costs. An interaction between personality disorders and common mental disorders significantly predicts increased total costs.