Symptom trajectories in intensive outpatient treatment exposure and response prevention for obsessive-compulsive...

Intensive Outpatient Program Exposure and Response Prevention (IOP EX/RP) is a highly effective intervention for obsessive-compulsive disorder (OCD), especially for those with greater support needs than outpatient therapy but less than residential treatment. However, patients exhibit heterogeneity in their treatment response to IOP EX/RP. This study aimed to characterize distinct patterns of obsessive-compulsive symptom change during IOP EX/RP and to identify clinical predictors of trajectory membership.

We explored weekly obsessive-compulsive symptom trajectories among 566 adults who had a diagnosis of OCD and received IOP EX/RP treatment. The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) was conducted at each week to assess patients' OCD symptoms. We conducted latent growth mixture modeling to explore the patterns of OCD symptom change across eight weeks of IOP EX/RP. Demographic characteristics, treatment modality, and psychiatric comorbidity were evaluated as predictors of trajectory membership using multinomial logistic regression.

Three distinct symptom trajectories emerged during the eight weeks of IOP, including a slow improvement trajectory (64.3%) characterized by gradual symptom reduction, a rapid improvement trajectory (22.3%) marked by pronounced gains, and a worsening trajectory (13.4%) characterized by symptom worsening over the same treatment window. Anxiety-, mood-, and OCD-related comorbidities significantly predicted less favorable early trajectories.

Despite the overall effectiveness of IOP EX/RP, patients follow distinct trajectories of symptom change during eight weeks of IOP EX/RP, evidencing the heterogeneity in affective and behavioral responses to evidence-based treatment. The findings underscore the importance of trajectory-informed monitoring to support personalized and adaptive treatment in intensive OCD care.