Unmeasured confounding is a common challenge in pharmacoepidemiological studies. Negative controls can be used to detect potential unmeasured confounding and thereby validate the reliability of study. Based on the Guidelines for Pharmacoepidemiological Research Methodology (2nd edition), this study systematically interprets the application of the negative control methods and related case studies. First, the definition and main types of negative controls are introduced, including negative exposure control, negative period control, and negative outcome control, clarifying their basic concepts and applicable scenarios. Second, it elaborates the primary purpose of this method, which is to identify and adjust for unmeasured confounding. Then, the implementation steps and statistical analysis methods are outlined, covering selection criteria during the study design phase and bias detection strategies during the statistical analysis phase. Finally, through detailed analysis of four types of typical cases, the practical application value of negative controls is demonstrated in areas such as verifying drug safety, evaluating effectiveness, and identifying and adjusting for unmeasured confounding. The study emphasizes that while negative controls may not eliminate bias, they serve as a supplementary analytical tool, when combined with other epidemiological methods, can effectively enhance the quality of causal inference in observational studies. This research provides methodological references for the appropriate selection and application of negative controls in pharmacoepidemiological practice, thereby contributing to the advancement of high-quality researches.

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