Previous research has found partial evidence for a role of personality traits in mental health outcomes. However, many of these studies do not examine all of the big 5 personality traits simultaneously, examine mental health generally, or a small number of mental health symptoms. These studies also tend to examine participants cross-sectionally, without examining the way in which personality traits may influence mental health longitudinally, after controlling for confounders. This study aims to overcome the previous patchwork coverage of this topic by combining a range of exposure and outcome variables in a prospective cohort study.