Anxiety and depression are common mental health conditions, and represent a major cause of distress and disability in young people. We do not yet understand a) which factors predict vulnerability in young people, b) what predicts who seeks treatment, or c) what characterises young people who respond to treatments compared to those who do not. We need to understand risk factors to allow us to target preventative efforts more effectively. Furthermore, understanding what determines who seeks treatment might allow greater outreach and support to be given to underserved populations, and understanding the factors determining treatment response may allow future research into novel treatments to be targeted, and greater clinical monitoring of those at risk of non-response. Performing this research in young people specifically is important: not only are young people at a critical point in life where they are forming relationships and making decisions about education and careers, but successful treatment access and response might also determine their future mental health. We propose to analyse data from the ALSPAC study, among others, to understand the factors affecting all these parts of young people’s mental health pathways. We also aim to produce an online, interactive, browser-based application that a) researchers, educators, clinicians and policy-makers can use to understand who to target prevention efforts towards, and b) so that young people and their families can have access to the same knowledge as those involved in treating them.