Development of a patient adherence scale for exposure and response prevention therapy.

Exposure and response prevention (EX/RP) is an evidence-based treatment for obsessive-compulsive disorder (OCD). For EX/RP to be maximally effective, it is believed that patients must adhere outside of sessions to the procedures they learn in therapy. To date, there is no standard measure of patient EX/RP adherence, despite the importance of accurately assessing EX/RP adherence in both clinical research and practice. This paper describes the development of the Patient EX/RP Adherence Scale (PEAS), which assesses the patient's between-session adherence to the therapist's EX/RP instructions, and presents initial data on the scale's reliability and validity. The scale was designed to focus on the key procedures of EX/RP and to be brief enough to be used at each treatment session. The scale demonstrates excellent interrater reliability and good face and content validity. The usefulness of the scale is considered in the context of being an important tool to researchers trying to understand and improve outcomes of EX/RP for OCD as well as to EX/RP therapists in clinical practice. Future research will need to test the scale's reliability and validity in a larger sample of patients over the course of treatment.