BACKGROUND The epidemiology of the association between psoriasis and inflammatory bowel disease is poorly defined and remains controversial.

AIM To evaluate the prevalence of inflammatory bowel disease in patients with psoriasis compared with the general population.

METHODS We searched the nationwide health claims database between 2011 and 2015 and evaluated the prevalence of inflammatory bowel disease, including Crohn's disease and ulcerative colitis.

RESULTS Prevalence of inflammatory bowel disease, Crohn's disease and ulcerative colitis in patients with psoriasis vs the general population in 2011 were 0.16, 0.05 and 0.12% vs 0.08, 0.03 and 0.06%, respectively, which increased significantly with time between 2011 and 2015. Patients with psoriasis consistently revealed higher standardized prevalence (age and sex adjusted) of inflammatory bowel disease, Crohn's disease and ulcerative colitis compared with the general population. Subgroup analysis revealed the highest risk of prevalent inflammatory bowel disease in patients younger than 19 years (crude odds ratio 5.33, 95% confidence interval 3.74-7.59). Severe psoriasis demonstrated higher odds of inflammatory bowel disease (odds ratio 2.96, 95% confidence interval 2.54-3.45) than mild psoriasis (odds ratio 1.68, 95% confidence interval 1.51-1.88).

LIMITATIONS Limited data for doing adjustment and cross-sectional study design.

CONCLUSIONS Psoriasis patients revealed higher risk of inflammatory bowel disease. In particular, young patients and those with severe psoriasis may require closer monitoring and comprehensive management.