Universal school‐based intervention targeting depressive symptoms in adolescents: A cluster randomized trial

We investigated the effects of three different interventions on depressive symptoms in adolescents. As a secondary aim, we explored the mediating role of social isolation, anxiety, sleep quality, and cognitive function of the intervention effect on depressive symptoms. We conducted a cluster randomized controlled trial, in which schools were randomly assigned to 1. Doubling physical education (PE) classes (3:20 h of PE/week); 2. Workshop with the PE teachers; 3. Workshop with the PE teachers + Doubling PE classes; and 4. Control group (1:40 h of PE/week). In total, 1279 adolescents were included, 56.4% females. Doubling PE classes and the workshop with the PE teachers + Doubling PE classes groups did not affect depressive symptoms (−0.947, 95% CI −3.176 to 1.281; and, 0.726, 95% CI −1.558 to 3.009, respectively). The workshop with the PE teachers decreased adolescents' depressive symptoms (−2.495, 95% CI −4.668 to −0.323), social isolation (−4.759, 95% CI −9.025 to −0.493), and poor sleep quality (−0.560, 95% CI −1.108 to −0.012) compared with the control group. Social isolation mediated 32% of the workshop effect on depressive symptoms. The workshop with the PE teachers and the workshop with the PE teachers + Doubling PE classes groups lowered in 93% and in 54% the risk of the adolescents in developing high depressive symptomatology compared with the control group, respectively. A workshop updating PE teachers on pedagogical and health‐related topics decreased depressive symptoms in adolescents. Moreover, improvements in the adolescents' social isolation mediated the effect of PE teachers' workshop intervention on the depressive symptoms in adolescents.