Finding Types of Research

What are Observational Studies?

"Observational designs are nonexperimental, quantitative designs. In contrast to experimental designs in which the investigator manipulates the independent variable and observes its effect, the investigator conducting observational research observes both the independent and dependent variables. In observational studies, variation in the independent variable may be due to genetic endowment, self-selection, or occupational or environmental exposures."

There are three types of observational study designs:

  • Case-control
  • Cohort
  • Cross-sectional

In a case-control study,

" participants are selected and categorized on the basis of the dependent variable (the outcome of interest). The purpose of the study is to test hypotheses about factors in the past (independent variables) that may explain the outcome."

With a cohort study,

"participants are measured or categorized on the basis of the independent variable and are monitored over time to observe occurrence of the dependent variable. In a cohort study, it is established at the outset that subjects have not already exhibited the outcomes of interest (dependent variable)."

And with a cross-sectional study,

"participants are observed only once, offering a 'snapshot' of the characteristics of interest at that particular moment."

Find Observational Articles

There are no filters for observational studies in the search system or databases. The best way to find these types of articles is to add a keyword of the study type to your search statement. Examples:

  • "heart disease" AND cohort
  • diabetes AND case-control
  • hypertension AND cross-sectional

There are also filters in specific databases that allow you to limit your search results to case reports, case studies or observational studies only.

Medline Complete: Publication Type Filter

Case Report, Case Study, Observational Study

To find observational studies in Medline, follow the steps below.

  1. Select the database link above to open the advanced search page.
  2. Enter your keyword(s) into the search boxes.  
  3. Move down to the Limit Your Results section. This is where you can add filters to your search to tell the database that you only want articles that fit specific criteria. 
  4. From the Publication Type menu, select either Case Reports, Case Study or Observational Study, as shown in the image below.

  1. After you have your results, make sure to read through the article abstracts to see which type of study design the researchers are using. There is no guarantee that the database will only generate these types of studies.

PubMed: Article Type Filter

Case Reports and Observational Studies

To find observational studies in PubMed, follow the steps below.

  1. Select the database link above.
  2. Enter your keyword(s) into the search box.
  3. Select Search.
  4. Select Additional Filters at the bottom of the filters list on the left-hand side of the page.
  5. This will generate a pop-up window where you can select Article Type and choose either Case Reports or Observational Study, as shown in the image below.



Note! With any of these searches, you will need to limit to full text to get articles immediately available to you.

Examples of Observational Studies