A school-based program to prevent depressive symptoms and strengthen well-being among pre-vocational students (Happy Lessons): Results of a randomized controlled trial

Background: Many adolescents experience depressive symptoms, with even higher prevalences among lower- educated Dutch students. Effective prevention programs for these students are scarce but needed. This randomized controlled trial (RCT) investigates the effectiveness of school-based prevention program Happy Lessons (HL) among Dutch pre-vocational students. Methods: Classes within schools were randomized to intervention (n = 124) or waitlist control group (n = 143). Students (n = 267, aged 11 to 15) completed questionnaires at baseline, 3- and 6-month follow-up. The primary outcome was depressive symptoms. Secondary outcomes were well-being and life satisfaction. Linear mixed models were executed, based on the intention-to-treat principle. Explorative analysis of the effect of HL on potential mechanisms such as class and school environmental variables was conducted. Trial registration: Dutch Trial Register NL9732. Results: This study found no statistically significant differences in favor of the intervention group on depressive symptoms (T1: Cohen's d [95 % CI] =-0.21[-0.49;0.07], T2:-0.20 [-0.48;0.08]), well-being (T1: 0.24 [-0.04;0.52], T2: 0.18 [-0.10;0.47]), life satisfaction (T1: 0.03 [-0.25;0.31], T2: 0.10 [-0.18;0.39]), classmate support (T1:-0.20 [-0.48;0.08], T2:-0.14 [-0.43;0.14]), school connectedness (T1:-0.08 [-0.36;0.20], T2: 0.20 [-0.08;0.49]), bullying others (T1: OR[CI] = 0.95 [0.68;1.32], T2: 0.92 [0.66;1.29]) and bullying victimization (T1: OR[CI] = 1.93 [0.73;5.15], T2: 1.61 [0.62;4.20]). Significant moderate effects were found on teacher support in favor of the intervention group at T1 (d[CI] =-0.37 [-0.65;-0.08]) and control group at T2 (d[CI] = 0.35 [0.07;0.64]). Conclusions: Further research should focus on the working mechanisms of school-based depression prevention programs and how to successfully implement these programs in the school context.