Psychotic disorders are amongst the most severe mental disorders. However, current treatments have failed to reduce disability or change the prospects for recovery for patients with a psychotic disorder. In this project, I will investigate an entirely novel therapy, targeting the core vulnerability profile of altered person-environment interactions underlying psychosis, specifically increased stress-reactivity and reduced motivated and goal-directed behaviour. My colleagues and I have developed a digital apparatus, the ‘PsyMate’, allowing real-time interventions for patients with severe mental illness. In this project, the PsyMate will be used to (1)reduce psychotic and emotional reactivity to stress with “detachment and acceptance” exercises in real life situations, and (2)improve motivated and goal-directed behaviour with real-time behavioural activation therapy. In a randomized controlled trial, I will investigate whether this self-management therapy, conducted outside the office in the patient’s real life, is capable of reducing psychotic reactivity to stress and of improving motivated behaviour in participants with an at-risk mental state for psychosis.In order to understand the impact of this intervention in terms of brain plasticity and prediction of response, I will use an experimental medicine approach to investigate the neural effects of the intervention. I will focus particularly on prefrontal dopamine-reactivity as the brain mechanism mediating altered person-environment interactions. In the current study, I will examine prefrontal dopamine reactivity towards positive as well as stressful negative events as the biological process mediating underlying motivated behaviour and environmental reactivity. Furthermore, I will investigate whether a self-management therapy specifically focused at aberrant person-environment interactions alters brain plasticity at the level of prefrontal dopaminergic neurotransmission in persons at risk for psychosis.