Patient Adherence as a Mediator of Cognitive Behavioral Therapy Outcome in Adults With Obsessive-Compulsive Disorder.

Exposure and response prevention (EX/RP) is a first-line treatment for obsessive-compulsive disorder (OCD), yet many patients fail to achieve full remission. Among the strongest predictors of treatment outcome is patient adherence-particularly to between-session exposure exercises and ritual prevention. However, limited research has examined factors that influence adherence. This study aimed to replicate and extend prior findings by identifying predictors of both treatment outcome and adherence among medicated adults with OCD undergoing EX/RP, and by evaluating adherence as a potential mediator of treatment outcome. The sample consisted of 121 adults with OCD who received a standard course of EX/RP over 8 weeks. Therapists rated patient adherence at each exposure session using the Patient EX/RP Adherence Scale. Potential predictors were identified based on existing literature and were tested individually; whether adherence mediated other significant predictors of outcome was tested in single mediation models. Greater patient adherence significantly predicted better treatment outcomes. Higher treatment expectancy and lower baseline avoidance significantly predicted greater adherence. Patient adherence fully mediated the relationship between treatment expectancy and treatment outcome, and also between baseline avoidance and treatment outcome. Patient adherence appears to be a key mechanism linking patient characteristics to EX/RP outcome. These findings underscore the importance of systematically monitoring and reinforcing adherence, proactively addressing avoidance, and enhancing treatment expectations to optimize treatment outcomes in EX/RP.