By carefully tracking 5,000 people after they have experienced a traumatic event, a just-launched NIMH-funded study aims to provide a finely detailed map of the array of factors that play a role in the development of mental disorders that occur in the wake of trauma. Information coming out of the study should provide a much deeper understanding of the mechanisms that give rise to post-traumatic disorders as well as a clearer basis for predicting who will be affected and how best to target treatment.