Association between schizophrenia and psoriasis: A two-sample bidirectional Mendelian randomization study.

BACKGROUND

Observational studies have showed an association between schizophrenia and risk of psoriasis and vice versa. However, whether schizophrenia is causally associated with psoriasis is unclear.

METHODS

A two-sample bidirectional Mendelian randomization (MR) analysis was performed with publicly available genome-wide association study data including schizophrenia (n = 77 096) and psoriasis (n = 462 933). The inverse-variance weighted method was performed as the main analysis, with a complementary with the other two analyses: MR-Egger and weighted median method. A series of sensitivity analyses were also conducted to evaluate the robustness of the results.

RESULTS

MR analyses indicated that genetically predicted schizophrenia was significantly associated with an increased risk of psoriasis [OR: 1.001, 95% confidence interval (CI): 1.000-1.002, p = 0.012]. However, no causal effect of genetically predicted psoriasis on schizophrenia (OR: 0.221, 95% CI: 0.029-1.682, p = 0.145) was detected. No pleiotropy or heterogeneity was detected in sensitivity analysis (all p > 0.05).

CONCLUSIONS

Our study provides genetic evidence for the causal association between schizophrenia and psoriasis.