Beautiful weights, misinterpreted effects: The use and misuse of overlap weighting in major medical journals, 2020-2025

Objectives. To evaluate the implementation and reporting practices of overlap weighting in major medical journals. Study Design and Setting. We reviewed observational studies published from January 2020 to May 2025 in five major medical journals (Annals of Internal Medicine, BMJ, JAMA, JAMA Internal Medicine, and NEJM) that used overlap weighting as a primary or sensitivity adjustment method. Reporting quality was assessed for estimand specification, definition of the overlap population, justification of the method, acknowledgment of advantages, and discussion of interpretability. Results. Seventeen eligible studies were identified. Four studies (24%) correctly named the estimand as the average treatment effect in the overlap population (ATO); two (12%) misreported the estimand as ATE, and the remainder did not specify an estimand. Ten studies (59%) described the overlap population at least partially. Sixteen studies (94%) highlighted at least one statistical advantage of overlap weighting, yet none acknowledged that results apply only to the overlap population. These results point to a notable gap in estimand reporting. Conclusion. Clearer specification of the estimand and its target population is essential to prevent misinterpretation. Strengthening reporting standards will support more transparent and appropriate use of overlap weighting in medical research.