Designing a measurement feedback system for personality disorders: Should outcome monitoring be based on symptom severity or personality functioning?

Measurement feedback systems (MFS) providing insight in treatment progress can improve mental healthcare outcomes. However, there is no uniform measurement feedback system that could be used to measure treatment progress for personality disorders (PD). This study compared two types of measures: a generic measure for symptom severity (Brief Symptom Index, BSI) and a specific measure for personality functioning (Severity Indices of Personality Problems, SIPP) at different points in time in order to provide insight in the most suitable measuring moment for a MFS for PD. This study is conducted in a sample of 996 Dutch PD patients (mean age 33.51 (SD 10.42), 73.1% female). Symptom severity and personality functioning were assessed before and multiple times during treatment, using a timespan of 24 months. Outcomes were examined over time using multilevel modeling. Symptom severity (generic measure) and personality functioning (specific measure) improved equally after 24 months. However, during these 24 months, different patterns of change were observed for symptom severity compared to severity of personality problems. In general, symptom severity decreased most during the 1st months of treatment, whereas personality functioning improved only after 6 months of treatment. A generic instrument of symptom severity is able to measure early changes in symptom distress but may not be able to measure longer term changes in personality functioning. The authors discuss policy implications for benchmarking using specific measures in the treatment of personality disorders.