After removing these outliers, a significant causal association was observed between Cystatin D and lung adenocarcinoma (OR = 1.178, 95% CI: 1.023–1.358, p = 0.023), while no significant causality was observed between cystatin M (prot‐a‐703) and squamous cell lung carcinoma (OR = 1.069, 95% CI: 0.949–1.206, p = 0.272) (Table S4). The gene discussed is CST5; the disease is lung adenocarcinoma.