Causal Relationship Between Colorectal Cancer and Common Psychiatric Disorders: A Two-sample Mendelian Randomization Study

Objective To elucidate the causal relationships between colorectal cancer (CRC) and prevalent psychiatric disorders through a two-sample Mendelian randomization approach.

Methods Utilizing publicly available genome-wide association study data, we explored the connections between CRC and various psychiatric disorders, including depression, anxiety, bipolar disorder, and schizophrenia. We applied three statistical analyses: inverse variance weighting, MR-Egger, and median weighting. Sensitivity analyses were conducted to ensure the reliability and validity of the results.

Results Inverse variance weighting analysis showed no significant links between CRC and depression (P=0.090), anxiety (P=0.099), or schizophrenia (P=0.899). Conversely, a significant inverse relationship was found with bipolar disorder (P=0.010).

Conclusion No causal connection exists between CRC and the psychiatric conditions of depression, anxiety, or schizophrenia. However, CRC may have a causal association with a reduced risk of bipolar disorder, further supporting the existence of the gut-brain axis.