Characterizing and predicting refractory rumination in obsessive compulsive disorder.

Rumination is problematic for individuals with obsessive compulsive disorder (OCD), and yet, is not addressed in standard treatment for OCD. Further, little is known about whether rumination improves following exposure and response prevention treatment and for whom. The present study sought to characterize the extent to which patients receiving partial hospitalization/residential treatment for OCD (N = 283) continued to struggle with rumination post-treatment. Next, baseline demographic and clinical data was used in two machine learning models to identify pre-treatment predictors of which patients were most likely to struggle with elevated rumination at discharge. Lastly, a mixed-effects model was used to assess the impact of elevated rumination at discharge on patients' OCD symptom severity at discharge, 1, 6, and 12-month follow up assessments. In this sample, rumination change from admission to discharge was minimal, and over one-third of patients did not experience any change in their rumination severity. Elastic net and random forest models predicted approximately 20 % of the out-of-sample predictive R2 using nested cross-validation, and both models identified baseline rumination as the strongest predictor of elevated post-treatment rumination. Rumination at discharge significantly predicted OCD severity at discharge, but this effect was not significant at the follow-up timepoints. These results suggest that rumination is problematic for individuals with OCD and is not sufficiently addressed for a significant portion of individuals.