Failures of self-control during conflicts between long-term goals and immediate desires are a key characteristic of many harmful behaviours, including unhealthy eating habits, lack of exercise and problematic substance use, which often have adverse personal consequences and incur great societal costs. The project aims to elucidate neurocognitive mechanisms mediating deficient self-control, both in daily self-control failures and in substance use disorders and behavioural addictions, which are characterized by a loss of control despite awareness of adverse consequences. We launched a prospective cohort study using a multi-level approach that combines (i) a comprehensive clinical assessment, (ii) behavioural task batteries assessing cognitive control and decision-making functions, (iii) task-related and resting state fMRI, and (iv) smartphone-based ecological momentary assessment of daily self-control failures. From a representative community sample, we recruited three groups of participants (n = 338; age 19 - 27) with (a) symptoms of non-substance related (n=118) and (b) substance-related addictive disorders (n=100) and (c) syndrome-free controls (n=120. Participants are invited to yearly clinical follow-up assessments and further multi-level assessments 3 and 6 years after initial recruitment. Results obtained so far (until 07/2021) provide converging evidence that task performance as well as brain activity in monitoring, control, and valuation networks is reliably associated with the propensity to commit real-life self-control failures. Results support a process model, according to which deficient performance-monitoring leads to an insufficient recruitment of control networks, which attenuates the impact of long-term goals on neural value signals and increases the likelihood of self-control failures. In the final funding period (until 06/2024), we will extend the clinical follow-up period to 7 years. In addition, we will assess stress markers as possible moderators of self-control. With our cross-lagged panel design we expect the project to make a substantial contribution to the central unresolved question whether dysfunctions of cognitive control are causally involved in the development and trajectories of self-control failures and addictive behaviours, as well as to the disputed question of communalities and differences between different addictive disorders. Thereby, we hope to contribute to mechanism-based models of self-control impairments as a foundation for improved prevention and therapy.