Study hypothesis: We hypothesize that copeptin will serve as a point of care tool to discriminate benign headache from potentially serious secondary headaches (e.g. subarachnoidal hemorrhage (SAH) or cerebral aneurysm, intracranial bleeding (ICB), brain tumor, vasculitis, meningitis) which require prompt hospitalisation and intervention. Based on copeptin values measured in other acute diseases, we assume a critical range between 5 and 20 pmol/l. The lower copeptin cutoff point of ≤ 5 pmol/l will have a sensitivity of ≥ 97% for ruling out serious secondary headache, and the higher cutoff point of ≥ 20 pmol/l will have a specificity of 90% to confirm serious NTH.