There are no generally accepted methods for preventing adolescent depression. Studies have tried to improve negative thinking with therapies such as Cognitive Behavioral Therapy (CBT), but this has been disappointing. The aim of our project is to study computerised tasks that measure more basic cognitive processes. These “automatic” cognitive processes occur implicitly, without conscious awareness. Previous studies in this area have mostly used self-reports of cognitive processing. They have also tended to be small cross-sectional samples so it is unclear whether such tasks can detect psychological vulnerability to future depression. We may find that adolescents who are less sensitive to positive “rewarding” information are at increased risk of future depression. If so, this would inform the development of preventive interventions such as electronic ‘apps’ that train adolescents to pay more attention to and respond more to positive information.