Examining the causal association between psoriasis and bladder cancer: A two-sample Mendelian randomization analysis

Background: Previous epidemiological observational studies have potentially associated psoriasis with bladder cancer, but the results are inconsistent, and the causality remains unknown. The present study aimed to examine whether there are causal associations between psoriasis and bladder cancer using bidirectional two-sample Mendelian randomization (MR) analysis. Materials and Methods: A two-sample MR analysis was conducted using publicly available genome-wide association study (GWAS) data for individuals diagnosed with psoriasis and bladder cancer. The inverse variance weighted (IVW) method was the primary method. The complementary methods used included the weighted median, MR-Egger, weighted mode, and simple mode methods. Heterogeneity and pleiotropy of the MR results were detected. Moreover, leave-one-out sensitivity analysis was also employed to evaluate the robustness and validity of the findings. Results: No significant causal association was detected between psoriasis incidence and the risk of bladder cancer using the IVW method (OR = 0.999, 95% CI 0.977-1.022; P = 0.956). Similarly, the IVW model revealed no evidence of a causal relationship between bladder cancer and the risk of psoriasis (OR = 0.979, 95%CI = 0.873-1.098; P = 0.716). The results of the complementary methods were consistent with those of the IVW method. There was no notable horizontal pleiotropy or heterogeneity (P > 0.05) in our MR analysis. The results of sensitivity analysis confirmed that the MR estimates were not driven by single-nucleotide polymorphisms (SNPs). Conclusion: This study does not support a causal relationship between psoriasis and bladder cancer.