Psoriasis and Risk of Colorectal Cancer: A Nationwide Population-Based Cohort Study in Korea

Background/Objectives: Psoriasis is a chronic systemic inflammatory disease associated with increased cancer risk; however, its relationship with colorectal cancer (CRC) remains unclear. This question is particularly relevant in Asia, where CRC incidence has been increasing rapidly in recent decades. Methods: We conducted a nationwide longitudinal cohort study using the Korean National Health Insurance Service–National Sample Cohort (2002–2019). Patients with psoriasis were identified using validated ICD-10 codes and matched 1:4 with controls by age, sex, income, and region. Propensity score overlap weighting was applied to achieve covariate balance. Incident CRC was defined using both ICD-10 codes and cancer-specific registration codes. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Results: A total of 16,670 patients with psoriasis and 66,680 matched controls were included. During follow-up, the incidence of CRC was comparable between the two groups. In the weighted model, psoriasis was not associated with an increased risk of CRC (aHR = 0.96; 95% CI: 0.83–1.10). Kaplan–Meier analysis showed no significant difference in cumulative incidence (log-rank p > 0.05). Subgroup analyses stratified by age, sex, income, region, and comorbidity burden yielded consistent null findings. Conclusions: In this large nationwide cohort, psoriasis was not associated with an increased risk of CRC. These findings suggest that psoriasis does not independently contribute to CRC risk at the population level and does not warrant additional CRC surveillance beyond established screening recommendations, even in a high-burden setting such as Korea.