Objective: The identification of personality disorder among psychiatric in-patients is important because of the effect on the course and outcome of illness. The introduction of a multiaxial approach to diagnosis, has resulted in a higher than previously reported rate of occurrence of personality disorder in a variety of psychiatric settings. A prevalence of personality disorder of 4.9% is reported in the official statistics for Irish psychiatric hospitals. The aim of this study is to determine the true prevalence of personality disorders in two Irish psychiatric hospitals, one public and one private, using a multiaxial approach to diagnosis.

Methods: The Standardised Assessment of Personality (SAP) is a validated, semistructured, informant based instrument that reliably generates diagnoses of personality disorder irrespective of current mental state. Over a four month period, 78 consecutive, first ever admissions to two hospitals were examined using the SAP.

Results: The prevalence of personality disorder in this population was 26%. There was no significant difference in the rate of personality disorder between the public and private institutions.

Conclusions: The prevalence of personality disorder amongst in-patients in both public and private psychiatric hospitals in Ireland is far higher than previously reported. This highlights the importance of a multiaxial approach to diagnosis in order to establish the true extent of psychiatric morbidity.