Case–control study

A study that starts with the identification of a group of individuals sharing the same characteristics (for example people with a particular disease) and a suitable comparison (control) group (for example people without the disease). All subjects are then assessed with respect to things that happened to them in the past, such as things that might be related to the subjects getting the disease that is under investigation. Such studies are also called retrospective as they look back in time from the outcome to the possible causes.