Effects of a school-based intervention on levels of anxiety and depression: a cluster-randomized controlled trial of the MindPower program in ten high schools in Norway

Background The previous decades have shown increased symptoms of depression and anxiety among adolescents. To promote mental health and reduce mental illness, the government of Norway has, as in other countries, pledged that all schools must incorporate life-skills education. We report results from an evaluation of MindPower, a modification of the Coping With Depression (CWD) course, delivered universally in the classroom to secondary high school students, aged 15–16 years, in one county in Norway. The aim of the study was to evaluate the effect of MindPower on symptoms of depression and anxiety. Methods We utilized a two-groups` delayed intervention design where 110 first year high school classes were randomized into one of two intervention groups (IG1 and IG2). IG1 participated in MindPower while IG2 served as a control group for four months until the intervention started also in this group. IG1 and IG2 responded to questionnaires before and after the eight weeks course, at the start of the first and the second booster session, and at the five months follow up. Questionnaires, including online versions of the Hopkins Symptom Checklist (SCL-8) and the Reynolds Adolescent Depression Scale (RADS-2:SF), were administered to 1673 out of a total of 2384 students. SCL-levels were also compared with those from a large population study (UngData). Results According to mixed model analyses, SCL-8 and RADS-2:SF showed significant baseline differences between IG1 and IG2. In IG1 and IG2, both SCL-8 and RADS-2:SF showed a small but significant increase in mean scores throughout the study period, with markedly lower mean scores among boys. The SCL-levels were first lower for both girls and boys and then after the completion of MindPower the SCL-levels, equal to the SCL-levels in UngData. Conclusions No effects of the intervention were found. This large universal school-based trial suffered from considerable drop-out of participants. Experiences from implementation and evaluation of universal mental health promotion and preventive school interventions are thoroughly discussed, including, preparation, resources, support, time, realistic expectations, teacher selection and training, implementation, research designs and more. Several empirically based, practical advices are presented. Clinical Trial registration 27/08/2018. Registration number NCT03647826