Impact of Sources of Strength on adolescent suicide deaths across three randomized trials.

Universal interventions are key to reducing youth suicide rates, yet no universal intervention has demonstrated reduction in suicide mortality through an RCT. This study pooled three cluster-RCTs of Sources of Strength (n=78 high schools), a universal social network-informed intervention. In each trial, matched pairs of schools were assigned to immediate intervention or wait-list. Six schools were assigned without a pair due to logistical constraints. During the study period, no suicides occurred in intervention schools vs four in control schools, that is, suicide rates of 0 vs. 20.86/100,000, respectively. Results varied across statistical tests of impact. A state-level exact test pooling all available schools showed fewer suicides in intervention vs. control schools (p=0.047); whereas a stricter test involving only schools with a randomised pair found no difference (p=0.150). Results suggest that identifying mortality-reducing interventions will require commitment to new public-health designs optimised for population-level interventions, including adaptive roll-out trials.