1 Human Development and Family Studies, The Pennsylvania State University, University Park, Pennsylvania, USA.
2 The Edna Bennett Pierce Prevention Research Center, The Pennsylvania State University, University Park, Pennsylvania, USA.
3 Concordia University, Montreal, Quebec, Canada.
4 Partnerships in Prevention Science Institute, Iowa State University, Ames, Iowa, USA.

The loss of John Schulenberg reverberates across the developmental and prevention sciences. In honor of his many contributions, this paper applies his ideas of developmental continuity and discontinuity to understand the process by which PROSPER delivered universal prevention programs (delivered in Grades 6 and 7) affect young adult outcomes. Guided by these developmental models, we deconstructed adolescent substance use initiation trajectories into two discrete phases-early and late adolescence, demarcated by substance use initiation levels at the end of 9th grade. We evaluated the effects of PROSPER interventions on these phases, and in turn, the effects of adolescent substance use initiation on young adult antisocial behavior, alcohol and drug use consequences, and depression symptoms. This sample included 1,984 young adults who participated in the PROSPER intervention trial in Grade 6 (two cohorts, 2002 and 2003), followed over 8 adolescent measurement occasions (Fall and Spring of Grade 6; Spring of Grades 7-12). Young adult outcomes were averaged across three waves (collected at ages 20, 23, and 25). PROSPER interventions were associated with reduced substance use initiation in early adolescence, but not escalation during late adolescence. In turn, substance use in both early and late adolescence was uniquely associated with young adult antisocial behavior, depression symptoms, and substance use consequences. PROSPER interventions were associated with young adult antisocial behavior and problematic substance use via reduced risk for early initiation status. Findings are discussed in terms of developmental continuity and discontinuity.