Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space surrounding the brain. SAH may occur spontaneously, or following traumatic brain injury. Spontaneous SAH is in 85% of cases caused by rupture of an outpouching (aneurysm) of an intracranial artery. This is called an aneurysmal SAH (aSAH). The main findings of the present thesis concerned the incidence of aSAH in Norway, and sex ...