The causal relationship of colorectal cancer on schizophrenia: A Mendelian randomization study

Comorbidities associated with psychiatric disorders often occur in patients with cancer. A causal effect of schizophrenia on cancer was observed using Mendelian randomization (MR) analysis. However, the causal effect of colorectal cancer on schizophrenia has not been studied using MR analysis. Therefore, we performed MR analysis to investigate the causal effects of colorectal cancer on schizophrenia. We performed "two-sample summary-data Mendelian randomization" using publicly available genome-wide association studies data to investigate the causal relationship between colorectal cancer (as exposure) and schizophrenia (as outcome). The inverse variance weighted method was used to calculate causal estimates. In 2 TSMR analyses, we reported that the odds ratios for schizophrenia per log odds increase in colorectal cancer risk were 6.48 (95% confidential interval [CI] of OR 1.75-24.03; P = .005) and 9.62 x 106 (95% CI of OR 1.13-8.22 x 1013; P = .048). Pleiotropic tests and sensitivity analysis demonstrated minimal horizontal pleiotropy and robustness of the causal relationship. We provide evidence for a causal relationship between the incidence of colorectal cancer and the development of schizophrenia through TSMR analysis.