The causal relationship between psoriasis and chronic obstructive pulmonary disease: A bidirectional mendelian randomization study

Although many studies have investigated the association between psoriasis and chronic obstructive pulmonary disease (COPD), the causal relationship between psoriasis and COPD is still unknown.We employed bidirectional Mendelian randomization to investigate the causal relationship between psoriasis and COPD. Genetic instruments for exposure were selected from two distinct genome-wide association study databases. Single nucleotide polymorphisms associated with exposures at the genome-wide significance level (p < 5 × 10^-8 ) and exhibiting low linkage disequilibrium (r^2 < 0.001) were chosen as instrumental variables. Causality was assessed using multiple MR methods, including Inverse-Variance Weighted (IVW), MR-Egger, Weighted Median, Simple Mode, and Weighted Mode. A significance level of p < 0.05 was considered statistically significant. Heterogeneity was examined using Cochran's Q test, and MR-Egger regression was employed to detect pleiotropy. The robustness and reliability of the results were further evaluated through leave-one-out analysis.We found a positive causal association between psoriasis and COPD [IVW: odds ratio (OR): 1.0006; p = 0.0056]. Heterogeneity and pleiotropy have not been discovered, so the results of the study are reliable. In the reverse analysis, no causal association between CPOD and psoriasis was found.Our findings revealed that psoriasis was associated with an elevated risk of COPD. However, no causal association between COPD and psoriasis was identified in our study.