Mediators and Predictors of Treatment Response in a Brief Online Intervention for Rumination and Worry

Abstract Background Repetitive Negative Thinking (RNT) is a key transdiagnostic mechanism underlying anxiety and depressive disorders, and targeting RNT specifically leads to improved treatment outcomes. There is a lack of research however into mechanisms of change in RNT-focused interventions and factors that predict treatment response. The aim of this study was to examine the mediators and predictors of outcome (RNT, depression, anxiety, and distress) in a brief online intervention for RNT in adults. Methods This study used secondary data from a Randomised Controlled Trial of the Managing Rumination and Worry Program (Joubert et al. in Beh Res Therapy, 168:104378, 2023) in which N = 137 adults with elevated levels of RNT were randomly allocated to a 3-lesson clinician-guided or self-guided version of the program delivered over 6 weeks, or a treatment-as-usual (TAU) control condition. Self-report measures of depression, anxiety, distress, and RNT were administered at baseline, post-treatment, and 3-month follow-up; RNT and distress were also measured prior to each lesson. Results Intention-to-treat linear mixed models showed a gradual reduction in RNT and distress over treatment in both active conditions, with the largest reductions in RNT occurring after the lessons containing the active treatment strategies (2 and 3). Structural equation modelling mediation analyses showed that reductions in transdiagnostic RNT mediated reductions in distress between Lessons 2 and 3, and reductions in rumination specifically mediated reductions in distress and depression between post-treatment and follow-up, but there was no consistent pattern of mediation by RNT throughout treatment. Finally, higher baseline symptom severity (particularly rumination) significantly predicted poorer post-treatment outcomes, while higher treatment expectancy and clinician guidance significantly predicted better post-treatment outcomes. Conclusion This is one of the first studies to examine mediators and predictors of change in a brief, online RNT-focused intervention for adults with elevated RNT. Further research in larger samples is needed, examining additional possible mediating and predictor variables and across more time points, to better understand how and for whom this intervention reduces RNT, anxiety and depression. Australian and New Zealand Clinical Trials Registration number: ACTRN 12620000959976. Date of registration: 25/09/2020.