It is frequently stated in the literature and considered to be common knowledge that 15–30% of people with PCS have not recovered by a year after the injury, but this estimate is imprecise because it is based on studies of people admitted to a hospital, the methodologies of which have been criticized.
Det bliver ofte angivet i litteraturen at 15-30 % af PCS-ramte ikke er kommet sig et år efter skaden, men dette estimat er upræcist fordi det er baseret på studier af folk indlagt på et hospital, hvorfor metodologien er blevet kritiseret.