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Clinical Study Types - for Librarians


Case-Control Studies
Definition from PubMed: Comparisons that start with the identification of persons with the disease or outcome of interest and a control (comparison, referent) group without the disease or outcome of interest. The relationship of an attribute is examined by comparing both groups with regard to the frequency or levels of outcome over time.

  • PubMed considers "Retrospective Studies" to be  a sub-category of Case-Control Studies

Definition from article ("Epidemiology in Practice: Case-Control Studies"): First, identify the cases (a group known to have the outcome) and the controls (a group known to be free of the outcome). Then, look back in time to learn which subjects in each group had the exposure(s), comparing the frequency of the exposure in the case group to the control group. from Epidemiology in Practice: Case-Control Studies by Susan Lewallen,


Case-control v Cohort (in layman's terms):

- case-control:  you know the outcome; are looking for information on exposures; reasons that someone might have a specific condition.  Backwards-looking.

- cohort study: you have information on exposures (person has the condition), you are looking for information on outcomes. Forward-looking.



Here are some examples of articles tagged with the MeSH term for Case-Controlled Studies:

  • Dissociative sensibility disorders - A retrospective case series and systematic literature review.
  • Association between diabetes and tuberculosis: case-control study.
  • Induced Abortion, Birth Control Methods, and Breast Cancer Risk: A Case-Control Study in China.

Where This MeSH Term Can Be Found in the MeSH 'Tree'

In PubMed, they are under Epidemiological Studies:

Consider Asking the Researcher

Since retrospective studies are listed under case-control studies in MeSH, ask the researcher if they are also interested in retrospective studies.  If so, it is probably worthwhile to search on that word (retrospective) separately as a keyword.


NCBI's StatPearls is a concise (2-page) description of what case control studies are, examples of when this type of study is appropriate, and basic statistics information used with case control studies.

Methodology Series Module 2: Case-control Studies is an in-depth article about case control studies.

Maps and Directions