Effectiveness of a blended school-based mindfulness program for the prevention of co-rumination and internalizing problems in Dutch secondary school girls: a Cluster Randomized Controlled Trial

Abstract Background: A growing body of literature indicates that adolescent girls who talk with close friends about interpersonal problems or worries in an excessive, speculative way and with an intense focus on distress (i.e., co-rumination ) are at heightened risk for developing internalizing symptoms and disorders as well as reduced friendship quality. However, to date, there are no prevention programs available that target high levels of co-rumination between adolescent girls. As such, we developed the blended school-based mindfulness prevention program Happy Friends, Positive Minds (HFPM) that targets co-rumination at the dyadic level, i.e., between two close female friends. The aim of this trial is to evaluate the effectiveness of HFPM to reduce co-rumination and internalizing problems and to enhance wellbeing and social-emotional behavior in Dutch adolescent girls. Methods : A cluster Randomized Controlled Trial (cRCT) will be conducted to evaluate HFPM effectiveness. We will recruit 160 female friendship dyads ( n = 320 girls) aged 13 to 15 years who will be characterized by high levels of self-reported co-rumination. The cRCT has two arms: (1) an intervention condition in which 160 girls (80 friendship dyads) will receive the 14-week HFPM program, and (2) a control condition in which 160 girls (80 dyads) will receive care-as-usual (CAU). Data will be collected at baseline (T0: October 2023), during the program (T1: December 2023; T2: February 2024; T3: April 2024), immediately after the program (T4: July 2024) and at one-year follow-up (T5: July 2025). Participant-level self-reported risk for (early onset) depression and anxiety, self-reported and observed co-rumination, self- and friend-reported friendship quality, self-reported positive and negative affect, self-reported interpersonal responses to positive affect and self-reported anhedonia symptoms will be the outcome variables. Discussion: This study will provide insights into the short-term and long-term effects of the HFPM program on girls’ internalizing problems, wellbeing and social-emotional behavior. Trials registration : International Standard Randomized Controlled Trials, identifier: ISRCTN54246670. Registered on 27 February 2023.