Fig. 1

Study design of the bidirectional mendelian randomization between depression and different types of cancer. The blue solid lines represent the association between the instrumental variables (SNPs) and exposure as well as the association between exposure and outcome. The red solid lines represent the association of reverse causality. Dash lines with cross means that the association meets two basic assumption of mendelian randomization: i) the genetic variants (SNPs) are independent of confounders between exposure and outcomes; ii) the genetic variants only influence outcome via exposure