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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.