This ERC-AdG project aims to understand hyperarousal, a key symptom of anxiety- and insomnia disorders, which account for more than half of the global mental health burden. Hyperarousal covers subjective, physiological and clinical indicators. Why do individual differences in hyperarousal determine severity, prognosis and treatment response across insomnia-, anxiety- and stress-disorders? The project combines large-scale data-driven approaches with targeted testing of the novel hypothesis that hyperarousal may be reset overnight. Crossing disciplines and diagnoses, the project will first deliver an integrated account of the subjective, brain structural, brain functional and physiological hyperarousal landscape. Second, the project will yield better tools to quantify hyperarousal. These tools will be employed in both experimental preclinical studies and immediately applicable transdiagnostic clinical interventions expected to considerably improve the perspectives of people suffering from the most common mental disorders by alleviating hyperarousal overnight.