LAUSR

OBJECTIVE Despite disease modifying therapies' (DMT) demonstrated efficacy for treating relapsing MS, around 40% of patients discontinue use. This study aimed to understand the mechanism of action of Motivational Interviewing plus cognitive behavioral therapy (MI-CBT) in a previously conducted randomized controlled trial in which the MI-CBT intervention successfully promoted DMT re-initiation of participants compared to a treatment as usual (TAU) condition. METHODS This secondary analysis (N = 91) explored changes in motivation (a single item motivation "ruler" [Mot∆], and the Brief Motivation Scale [BMS∆]), autonomous motivation (AR∆), personal control (PC∆), treatment control (TC∆), and confidence to reinitiate (Con∆) as potential mediators of the treatment effect, using logistic regression. RESULTS Logistic regression analysis including all potential mediators as predictors of initiation indicated the BMS∆ was the only statistically significant predictor (OR = 1.61, p = 0.010). When BMS∆ was removed Mot∆ (OR = 1.22, p = 0.002) and PC∆ (OR = 1.67, p = 0.002) were statistically significant predictors of initiation. CONCLUSION The MI-CBT intervention appeared to work primarily by increasing motivation to initiate DMT.