The Happy Friends, Positive Minds randomized controlled trial addressing excessive co-rumination in Dutch adolescent girls.

The adolescence is a vulnerable period characterized by the search for identity and autonomy. Close peer friendships become of critical importance, implying important influences on emotion regulation during stress, including the regulation of both affective and physiological responses. Self-disclosure, something to which girls are more inclined than boys, becomes an
important emotion regulation strategy. Self-disclosure between close female friends escalating into co-rumination, implies benefits as well as risk on the individual and dyadic level: co-rumination enhances the quality of friendships among female adolescents, while simultaneously increasing the risk of internalizing problems. Currently, there are no evidence-based targeted prevention programs available aimed at preventing excessive co-rumination and internalizing problems in girls. The Happy Friends, Positive Minds (HFPM) cRCT evaluates the short-term and long-term effect of the HFPM school-based mindfulness program in a sample of 320 Dutch girls aged between 13 to 15 years. This program primarily aims to support girls in developing different evidence-based mindfulness skills on the dyadic level. This program comprises a weekly training, guided by the ‘Happy Friends app’, which support the development of mindfulness skills in their daily life. Data will be gathered at six different time points over a span of 2 years, commencing with
a baseline measure and ending with a 1-year follow-up. We will measure the degree of anxiety and depressive feelings, as well as a sense of control over one's own life and the quality of friendships. Secondarily, HFPM aims to study how implementation factors will impact the effectiveness of this prevention program.