Early adolescence is a sensitive period of significant social and physiological growth, and represents the time when symptoms of mental disorders commonly emerge. Clinical staging models have been proposed to provide framework for identifying early risk factors and symptoms in adolescence and young adulthood, that may predict future progression to mood disorders and psychosis. It has been suggested that sub-threshold symptoms may be predictive of later stages of more serious mental disorders. We propose to examine the associations between parent rated sub-threshold mental health symptoms in early adolescence and mental health symptom stages in young adulthood. This will help determine which of these symptoms could represent risk of progression to stages associated with need for care. Parents offer unique insight into early mental health symptoms, observing their children in a home environment. It is important to understand the trajectories associated with parental accounts. If specific parent rated sub-threshold symptoms in early adolescence can be identified, that are predictive of progression to later stages of mood, anxiety and psychotic symptom stages in young adulthood, this could provide understanding of prognosis and intervention needs to adolescents and their families. Cannabis use, alcohol use and negative life events may mediate the relationship between parent rated symptoms in early adolescence and mental health difficulties in young adulthood. We propose to analyse these pathways in order to understand whether these factors are associated with increased risk of progression to later clinical stages. This project will contribute to understanding the validity of clinical staging models for psychotic and mood disorders in youth mental health, in particular contributing to understanding of early risk factors in these models, and could provide opportunities for targeted intervention and prevention.