A case-control study is a type of observational research commonly used in epidemiology to identify factors or exposures that may be associated with a specific outcome, typically a disease or condition. This is done by comparing a group of patients who have the disease or condition (cases) with a group of people who do not have it (controls) but who are otherwise as similar as possible (in characteristics thought to be unrelated to the causes of the disease or condition).
This study design is particularly useful when studying rare diseases or outcomes, where it might be impractical to conduct a large cohort study.