Tomczyk Samuel In Programme October, 23 11:50 to 13:20 October, 23 16:00 to 17:30 Hours & Dates Wednesday, October 23 11:50 Mechanisms and outcomes in substance use prevention among youth11:50 to 13:20Room 5AOral presentation session Wednesday, October 23 16:00 Keynote presentation Evidence-based prevention through collaborative action? Opportunities and challenges for community-based participatory research in prevention science 16:00 to 17:30 Auditorium I Samuel Tomczyk