Evidence is not always available via filtered resources. Searching the primary literature may be required. Learn more about each type of study below and the relevant databases where you can find each study type.
In RCTs, study participants are randomly assigned to one of two intervention groups.
Cohort studies are a type of medical study used to investigate the causes of disease, establishing links between risk factors and health outcomes. These studies examine cohorts of people before the occurrence of certain outcomes. They study causation, so they are usually forward-looking - that is, they are "prospective" studies, or planned in advance and carried out over a future period of time.
Cohort studies, especially prospective studies, are often also referred to as longitudinal because of the length of time it takes to observe the study population.
Case Control studies serve the purpose of comparing patients with a particular disease/condition (cases) with patients who do not (controls). Researchers then look retrospectively to compare medical histories and records of both patient groups to identify potential exposures and risk factors present in each group. This seeks to determine a relationship between a given risk factor and a disease.
No intervention, treatment, or drug is administered during this study - it is purely observational. These retrospective studies are meant to estimate odds or likelihood of individuals potentially developing a condition due to exposure to a particular risk factor.
Case control studies are commonly referred to as 'retrospective studies' and 'case-referent studies' (Himmelfarb Health Sciences Library).