Here's a search string to return Observational Studies in PubMed:
("Epidemiologic Studies"[Mesh] OR "Observational Study" [Publication Type]
OR "epidemiologic study" OR "epidemiologic studies"
OR "observational Study" OR "observational studies"
OR “cohort study" OR "cohort studies"
OR "case-control study" OR "case-control studies"
OR "cross-sectional study" OR "cross-sectional studies" OR prospective OR retrospective OR longitudinal)
Ovid has a filter: https://tools.ovid.com/ovidtools/expertsearches.html which translated to PubMed is: "Epidemiologic Studies"[Mesh] OR “case control” OR “cohort study” OR “cohort studies” OR “cohort analysis” OR “cohort analyses” OR “follow-up study” OR “follow-up studies” OR “observational study” OR “observational studies” OR longitudinal OR retrospective OR cross sectional
(the MeSH terms for Case Control studies, Cohort studies and Cross-Sectional studies are underneath Epidemiologic Studies, so it’s not necessary to search on them separately as well)
Differences: mine includes the terms "Observational Study" [Publication Type], "epidemiologic study," "epidemiologic studies," "observational Study," "observational studies," and prospective. Also, Ovid searches on the terms ‘case control’ and ‘cross sectional’ while I search on those terms as a phrase with the words ‘study’ or ‘studies’ included.
Ovid's filter:
Epidemiologic studies/
Exp case control studies/
Exp cohort studies/
Case control.tw.
(cohort adj (study or studies)).tw.
Cohort analy$.tw.
(Follow up adj (study or studies)).tw.
(observational adj (study or studies)).tw.
Longitudinal.tw.
Retrospective.tw.
Cross sectional.tw.
Cross-sectional studies/
Or/1-12
Observational Studies is a broad area. It is one of the two categories that clinical studies are often divided into: Observational studies or Interventional studies.
Observational study types include Cohort, Case-Control and Cross-Sectional studies (among others). Observational studies are sometimes called Epidemiological studies.
In PubMed, the study types listed above are categorized as Epidemiologic Studies.
While there is a MeSH term for Observational Study, if you are searching for observationals studies we recommend you use the MeSH term for 'Epidemiologic Studies' instead. There are over 2.6 million articles tagged with the MeSH term 'Epidemiological Studies;' but only about 100,000 articles tagged with the MeSH term 'Observational Study.' 'Observational Studies' was introduced in 2014 and MEDLINE does not retrospectively tag articles, which is one probably reason why there are comparatively few articles tagged wtih this MeSH term.
Recommended: to find "Observational Studies" in PubMed, search both MeSH terms:
("Epidemiologic Studies"[Mesh] OR "Observational Study" [Publication Type])
You will want to add keywords to the above search string; this may be a good start. See box to the left for a modifiable search string.
Mesh database definition for Observational Studies:
Observational Study [Publication Type]
A work that reports on the results of a clinical study in which participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to specific interventions (as in an interventional study). Year introduced: 2014
MeSH database definition for Epidemiologic Studies:
Epidemiologic Studies
Studies designed to examine associations, commonly, hypothesized causal relations. They are usually concerned with identifying or measuring the effects of risk factors or exposures. The common types of analytic study are CASE-CONTROL STUDIES; COHORT STUDIES; and CROSS-SECTIONAL STUDIES. Year introduced: 1998
Below are the MeSH trees for both terms.
PubMed splits Observational Studies into two areas: As Topic and Publication Type. Which to use? If you're doing a systematic review, use [publication type]. Basically, "Publication Type" means it's an article about the results of a trial. "As Topic" means it's about the general topic of trials: maybe how to recruit patients, or how to conduct a specific aspect of a trial. Here are the official MeSH defiitions:
Observational Studies as Topic: Works about clinical studies in which participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to specific interventions (as in an interventional study). Year introduced: 2014
Observational Study [Publication Type]: A work that reports on the results of a clinical study in which participants may receive diagnostic, therapeutic, or other types of interventions, but the investigator does not assign participants to specific interventions (as in an interventional study).Year introduced: 2014
Examples of articles that were tagged with each MeSH term:
Publication Type: (these are probably the types of articles you want)
As Topic: (you probably don't want these articles returned in your search results)
Cochrane Database Syst Rev. 2019 Mar; 2019(3): Search strategies to identify observational studies in MEDLINE and Embase
also check out UT: https://libguides.sph.uth.tmc.edu/search_filters/ovid_medline_filters
these are from ISSG's list: https://sites.google.com/a/york.ac.uk/issg-search-filters-resource/home/observational-studies