Adherence
Therapists registered whether patients attended the booster consultations and whether they completed the homework assignments in MS Stay Fit. Log data of the online platform provided information about which booster modules were opened and completed. Treatment adherence for the booster condition was defined as attending at least one booster consultation, since some patients may not need a second booster session in case they did not profit from CBT, or if they felt confident about sustaining treatment effects. Reasons for not attending a second booster session were noted.All study participants were requested to complete the follow-up questionnaires at weeks 39 and 52.