Differential Causal Effects of Common Analgesics on Breast Cancer Risk and Survival: Evidence from Mendelian Randomization

This MR study links a genetic predisposition to paracetamol use with increased breast cancer risk (especially ER+), and to aspirin use with improved survival. These divergent findings point to drug-specific mechanisms, warranting caution with long-term paracetamol use and further study of aspirin's therapeutic potential. Clinical decisions should balance analgesic benefits against these potential cancer-related outcomes.