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Clinical Study Types - for Librarians

Observational vs Interventional

Clinical research studies are often divided broadly into two types:

  • observational (or epidemiological) studies
  • experimental (or interventional) - sometimes just called Clinical Trials

Observational (or Epidemiologic) Studies

Observational Studies/ Epidemiological studies
"In observational studies, as the name suggests, the observer only observes as such or with tools/relevant investigations and does not interfere with the natural course of the disease/clinical condition. Observational studies are cross-sectional, case control or cohort studies." Observational study designs, also called epidemiologic study designs, are often retrospective and are used to assess potential causation in exposure-outcome relationships and therefore influence preventive methods. 

PubMed has MeSH terms for Observational Studies and Epidemiologic Studies.  Their "Observational Studies"[Publication type] MeSH term has no subcategories, was introduced in 2014 and has a very small fraction of the results that Epidemiologic Studies has. The types of studies usually considered Observational (cross-sectional, case control or cohort studies) show up in MeSH under Epidemiological.  For more information on this please refer to the guide for Observational Studies, using the tabs to the left.


Interventional Studies

Interventional / Experimental / Clinical Trials

A clinical trial is an interventional or experimental study, where the investigator intervenes with treatment or determines the exposure to identify how one treatment arm fares in comparison to the other, the intervention actually changes the progress of the disease.  THe most common type of Interventional Trial is a randomized controlled trial.


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