We found that the indirect effect of DHA (22:6) levels in the causal pathway from CTSH to lung adenocarcinoma was 0.0009 (95% CI 4.3e‐5‐0.002, p = 0.0397), with a corresponding mediation proportion of 1.16% (95% CI 0.05% ‐ 2.26%). This evidence concerns the gene CTSH and lung adenocarcinoma.