Mechanisms of symptom reduction in treatment for obsessions.

Objective: We explored the dynamic relationship between cognition and obsession severity during 2 different treatments for primary obsessions, examining evidence for the hypothesis that symptom reduction would be mediated by appraisals about the meaning of unwanted intrusive thoughts.
Method: Data from a recent randomized controlled trial were analyzed with traditional mediation analyses and latent difference scores. The trial had compared cognitive behavioral therapy and stress management training among 73 patients with primary obsessions. Mediation analyses were conducted with pre-, post-, and follow-up scores on the Obsessions subscale of the Yale-Brown Obsessive Compulsive Scale and 2 self-report measures of cognitions related to obsessive-compulsive disorder. Bivariate dual change score (BDCS) analyses were conducted with weekly assessments of obsession severity and appraisals of personal significance.
Results: Change in most cognitions related to obsessive-compulsive disorder accounted for reduction in obsession severity during the course of treatment and follow-up. BDCS analyses of the longitudinal data, however, indicated prior obsession severity is a leading indicator of subsequent change in appraisals, rather than the reverse. Analyses also suggested cognitive behavioral therapy is more effective than stress management training when symptoms are severe and that stress management training is more advantageous in the context of mild-to-moderate obsessions.
Conclusions: The traditional mediation analysis indicated that appraisal change is a tenable mediator of obsession reduction, but the BDCS results raise doubts about the causal direction. The results highlight the importance of examining the dynamic relationship between putative mediators and outcome variables, and they suggest interesting hypotheses about mechanisms in treatment of obsessions.