Ecological fallacy — MRCPsych Paper A MCQ

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ModerateEpidemiology and research methodsEcological fallacyMRCPsych Paper A

An observational study finds that countries with higher population rates of antidepressant prescribing have lower suicide rates. Without analysing linked individual-level data, the authors conclude that individuals prescribed antidepressants have a lower risk of suicide. Which methodological error have the authors made?

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Correct answer: C — Ecological fallacy

The correct answer is C, ecological fallacy. The study identifies an association between aggregate national prescribing and suicide rates but then applies that relationship to individual patients. Group-level associations may differ from, or even reverse, associations at the individual level; linked individual-level data would be needed to support that conclusion. Recall bias concerns inaccurate recollection of past exposures or events. The Hawthorne effect is behavioural change caused by awareness of being observed. Observer bias occurs when investigators' expectations influence measurement or recording. Regression dilution is attenuation of an estimated association due to random measurement error in an explanatory variable. None of these alternatives describes inappropriate inference from countries to individuals.

Reference: Sheppard L. Insights on bias and information in group-level studies. Biostatistics. 2003;4(2):265–278. https://pubmed.ncbi.nlm.nih.gov/12925521/