(retrospective) Studies that look back using observations collected predominantly prior to subject selection and enrollment. (clinicaltrials.gov)

(retrospective study) A research method that looks for possible causes for a current disease by examining a study population's past habits.

(retrospective study) A study in which participants with known outcomes are assessed based on data collected before the study.

(retrospective study) A study that compares two groups of people: those with the disease or condition under study (cases) and a very similar group of people who do not have the disease or condition (controls). Researchers study the medical and lifestyle histories of the people in each group to learn what factors may be associated with the disease or condition. For example, one group may have been exposed to a particular substance that the other was not.

(retrospective study) A study with planned observations collected predominantly before study start (i.e. backward-looking). Note: Examples are case-control studies or retrospective cohort studies when the observations from the selected subjects occurred before study start.

Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.