This Viewpoint presents considerations for assessing evidence for causal inference when using sophisticated study designs with regression analyses of longitudinal observational data. A view is sometimes expressed that regressions with observational data can never give causal conclusions. I argue this position is too extreme. While observational data rarely conclusively demonstrate causality, some study designs may provide evidence, and sometimes that evidence can be strong. However, the extent of evidence depends on a number of considerations. These considerations are narrower than those discussed decades ago by Hill,1 which covered evidence from numerous sources, not just that from observational studies. I will begin with considerations concerning regression analysis using a single observational study and then return to broader considerations on the synthesis of evidence across studies.
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VanderWeele TJ. Can Sophisticated Study Designs With Regression Analyses of Observational Data Provide Causal Inferences? JAMA Psychiatry. 2021;78(3):244–246. doi:10.1001/jamapsychiatry.2020.2588
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