The impact of co-morbid personality disorder on use of psychiatric services and involuntary hospitalization in people with severe mental illness.

PURPOSE: To examine the impact of co-morbid personality disorder (PD), on inpatient and community-based service use and risk of involuntary hospitalization, amongst patients with severe mental illness (SMI).
METHODS: We identified SMI cases (schizophrenia, schizoaffective and bipolar disorder) with and without co-morbid PD, and PD cases, aged ≥18 years, in a large secondary mental healthcare case register. Using multivariable logistic regression, we examined the association between co-morbid PD and high level of inpatient and community-based service use (defined as the top decile of service use), and involuntary hospitalization, respectively, adjusting for socio-demographics, clinical symptoms and social functioning.
RESULTS: Severe mental illness patients with co-morbid PD (SMI-PD) (n = 961) had more severe symptoms and social functioning problems compared to SMI patients without PD (n = 10,963) and patients who had PD but no concurrent SMI (n = 2,309). A greater proportion of SMI-PD patients were high inpatient service users (22.4 vs. 10.1 %). This association was attenuated but remained significant, after adjustment (fully adjusted odds ratio, OR 2.31, 95 % CI 1.88-2.84). The association between SMI-PD and high community-based service use was confounded by symptoms and social functioning. Compared to patients with SMI, SMI-PD patients were significantly more likely to experience involuntary hospitalization (fully adjusted OR 1.56, 95 % CI 1.31-1.85).
CONCLUSIONS: In SMI patients, co-morbidity with PD is robustly associated with both high use of inpatient psychiatric services and an increased likelihood of involuntary hospitalization. Patients with SMI and co-morbid PD are likely to require tailored interventions that target both the underlying personality pathology as well as the Axis I disorder.