The Inter-Venture Trial is a cluster-randomised controlled trial of three intervention modalities developed involving active youth, family and community engagement in the Montreal area: (i) Systematic school-based screening and early personality-targeted interventions for students most at risk of mental health problems and substance misuse (Preventure program); (ii) Community-based parent training program and (iii) Timely and integrated services provided by a multidisciplinary team of professionals (Inter-Action).