biostudies-literatureUnknown12(1)Sun YPsoriasis is more common in patients with inflammatory bowel disease (IBD) than in the general population. Similarly, patients with psoriasis or psoriatic arthritis (PsA) have a higher incidence of IBD. However, whether this association is causal remains unknown. Therefore, we used a two-sample bidirectional Mendelian randomization (MR) analysis to identify this relationship. According to MR analysis, psoriasis and PsA causally increased the odds of developing Crohn's disease (OR = 1.350 (1.066-1.709) P = 0.013; OR = 1.319 (1.166-1.492) P < 0.001). In contrast, MR estimates gave little support to a possible causal effect of psoriasis, PsA, on ulcerative colitis (OR = 1.101 (0.905-1.340) P = 0.335; OR = 1.007 (0.941-1.078) P = 0.831). Similarly, the reverse analysis suggested the Crohn's diScientific reports20526https://www.ebi.ac.uk/biostudies/studies/S-EPMC9705442biostudies-literatureThe causal relationship between psoriasis, psoriatic arthritis, and inflammatory bowel diseases.PMC9705442Li YZhang JSun YfalseThe causal relationship between psoriasis, psoriatic arthritis, and inflammatory bowel diseases.Psoriasis is more common in patients with inflammatory bowel disease (IBD) than in the general population. Similarly, patients with psoriasis or psoriatic arthritis (PsA) have a higher incidence of IBD. However, whether this association is causal remains unknown. Therefore, we used a two-sample bidirectional Mendelian randomization (MR) analysis to identify this relationship. According to MR analysis, psoriasis and PsA causally increased the odds of developing Crohn's disease (OR = 1.350 (1.066-1.709) P = 0.013; OR = 1.319 (1.166-1.492) P < 0.001). In contrast, MR estimates gave little support to a possible causal effect of psoriasis, PsA, on ulcerative colitis (OR = 1.101 (0.905-1.340) P = 0.335; OR = 1.007 (0.941-1.078) P = 0.831). Similarly, the reverse analysis suggested the Crohn's di2022-01-01T00:00:00Z2022 Nov2025-04-26T09:40:44.178Z2025-04-06T13:08:50.174ZS-EPMC97054423644338410.1038/s41598-022-24872-5