We need to start thinking about thinking: The impact of rumination on OCD symptom improvement in exposure and response prevention.

While rumination has been recognized in clinical settings as prevalent and problematic for individuals with obsessive compulsive disorder (OCD), its relationship to OCD symptom trajectories has been understudied. In a large sample of N = 315 adults receiving exposure and response prevention (ERP) for OCD we evaluated the relationship between rumination and OCD symptoms. In our first aim, we characterized change in rumination across treatment and calculated the percentage of patients exhibiting change in rumination. In aim 2, we characterized how change in rumination impacts OCD symptom trajectories across treatment using a linear mixed-effects model. We found a significant interaction between rumination change (pre- to post-treatment) and week of treatment on weekly OCD severity measures, such that patients who experienced less improvement in rumination also experienced less weekly improvement in their OCD symptoms. In aim 3, we evaluated random-intercept cross-lagged panel models (RI-CLPMs) to assess how changes in rumination and OCD symptoms reciprocally affect each other across weeks of treatment. We found that autoregressive, cross-sectional, and cross-lagged relations between rumination and OCD symptom severity explained week-specific deviations from patient's own average symptoms independently of the between-person relations between rumination and OCD symptom severity. Rumination did not change for a significant number of patients receiving ERP, and these results demonstrate that lack of improvement in rumination affects OCD symptom trajectories. Given the hypothesized function of rumination as an emotional avoidance strategy, future research should evaluate the potential benefits of targeting rumination directly towards enhancing treatment outcomes for OCD.