Editing Case–control study (section)

==Strengths and weaknesses==
Case–control studies are a relatively inexpensive and frequently used type of epidemiological study that can be carried out by small teams or individual researchers in single facilities in a way that more structured experimental studies often cannot be.  They have pointed the way to a number of important discoveries and advances. The case–control study design is often used in the study of rare diseases or as a preliminary study where little is known about the association between the risk factor and disease of interest.<ref>{{cite journal | vauthors = Levin KA | title = Study design I | journal = Evidence-Based Dentistry | volume = 6 | issue = 3 | pages = 78–79 | year = 2005 | pmid = 16184164 | doi = 10.1038/sj.ebd.6400355 | doi-access = free }}</ref>

Compared to prospective [[Cohort study|cohort studies]] they tend to be less costly and shorter in duration. In several situations, they have greater statistical power than cohort studies, which must often wait for a 'sufficient' number of disease events to accrue.{{citation needed|date=May 2023}}

Case–control studies are observational in nature and thus do not provide the same level of evidence as [[randomized controlled trials]]. The results may be confounded by other factors, to the extent of giving the opposite answer to better studies. A meta-analysis of what was considered 30 high-quality studies concluded that use of a product halved a risk, when in fact the risk was, if anything, increased.<ref name="pmid15166201">{{cite journal |vauthors=Lawlor DA, [[George Davey Smith|Davey Smith G]], Ebrahim S | title = Commentary: the hormone replacement-coronary heart disease conundrum: is this the death of observational epidemiology? | journal = Int J Epidemiol | volume = 33 | issue = 3 | pages = 464–7 | year = 2004 | pmid = 15166201 | doi = 10.1093/ije/dyh124 | doi-access = free }}</ref><ref name="pmid16014596">{{cite journal | vauthors = Ioannidis JP | title = Contradicted and initially stronger effects in highly cited clinical research | journal = JAMA | volume = 294 | issue = 2 | pages = 218–28 | year = 2005 | pmid = 16014596 | doi = 10.1001/jama.294.2.218 | doi-access =  | s2cid = 16749356 }}</ref> It may also be more difficult to establish the timeline of exposure to disease outcome in the setting of a case–control study than within a prospective cohort study design where the exposure is ascertained prior to following the subjects over time in order to ascertain their outcome status. The most important drawback in case–control studies relates to the difficulty of obtaining reliable information about an individual's exposure status over time. Case–control studies are therefore placed low in the [[hierarchy of evidence]].{{citation needed|date=May 2023}}