The peak period of risk for onset of mental illness including mood disorders extends from childhood into early adulthood, coinciding with a critical time of accelerated brain, psychological and social development. Therefore, illness during this developmental period is associated with a significant burden including school failure, problems in relationships, substance misuse and self-harm. Longitudinal study of informative populations over the peak period of risk provides an opportunity to map the emergent illness course, profile those at highest risk and identify targets for early intervention. This presentation will highlight key findings from research in two complementary and informative cohorts: high-risk offspring of bipolar parents and first year university students. Given the high estimated heritability of bipolar disorder, offspring of affected parents are a readily identifiable familial at risk group for the development of mood disorders. Whereas, university students, who increasingly resemble the broader emergent adult population, are in the peak developmental period of risk for illness onset. Therefore, prospective longitudinal studies of well-characterized high-risk offspring and university students can inform the prediction and early identification of mood disorders from complementary perspectives. Specifically, updated findings from the Canadian Flourish high-risk offspring cohort study and the newly launched U-Flourish first year university student cohort study will be presented. In addition, plans for future development of this longitudinal high-risk research will be outlined including planned collaborations with the University of Oxford.