Intermittent Motivational Interviewing and Transdiagnostic CBT for Anxiety: A Randomized Controlled Trial.

Recent meta-analytic findings suggest that Motivational Interviewing (MI) used as an adjunct to Cognitive Behavior Therapy (CBT) for anxiety disorders improves overall treatment outcomes (Marker & Norton, 2018). However, when used as a prelude to CBT, MI significantly increases the length of treatment and numerous studies note that the effectiveness of pre-treatment MI subsides over time. The current study adapted an already established 12-session transdiagnostic CBT protocol (tCBT, Norton, 2012) to include one hour of MI spread across four sessions of tCBT (sessions 1, 3, 8, and 10) at 15 minutes each, with the option of including additional MI if resistance arose in therapy. Thirty-six treatment seeking adults with principal anxiety disorder diagnosis were randomly assigned to receive intermittent MI and tCBT (iMI + tCBT) or tCBT and psychoeducation. Results indicated that the iMI + tCBT condition significantly outperformed the tCBT condition on several primary outcome variables. While no significant difference was found between the two groups on clinician rated scores of participant principal anxiety disorder, differences were found on a composite index of participants' self-report measures of symptom improvement, and on clinician rated scores of global psychiatric functioning. These effects were not moderated by baseline motivation or baseline ambivalence. The study also found that the iMI + tCBT condition showed significantly greater improvement to comorbid conditions and greater reduction in self-report depressive symptoms. The inclusion of MI did not impact participant drop out. This study provides further support for integrating MI and tCBT and highlights that even small doses of MI can improve treatment outcomes, without increasing length of usual therapy. Limitations and future research options are also discussed.