A large body of research has shown adverse childhood experiences (such as parental neglect, mental and physical abuse) can impact children’s developmental trajectories and have lasting effects on their cognitive function and mental health. In comparison, there is little consensus as to what types of adversity affect adolescents and the timing at which young people are most vulnerable to different types of adversity. This impedes the development of effective policies for prevention and intervention. Initial evidence suggests that for adolescents, other types of adversity, such as social exclusion by peers, may be particularly detrimental. With respect to timing of adversity, protracted sensitive periods of brain development in areas underlying complex skills, e.g., flexible thinking and building relationships, could present a window of vulnerability where young people are particularly sensitive to adversity exposure. The aims of this research project are twofold. First, to investigate what types of adversity impact cognitive and mental health outcomes in adolescents, and secondly, to determine when different adversities have the greatest impact. This will provide an opportunity for informing policies on how we can prevent and alleviate adversity in youth.