Risk of mood disorders in patients with colorectal cancer

Background: To assess the risk of mood disorders among patients with colorectal cancer (CRC), a population based cohort study was performed using the Taiwanese National Health Insurance Research Database. Methods: The study cohort included 27242 patients diagnosed with CRC between January 1, 2000 and December 31, 2010. Four insurants from the general population without CRC were frequency matched to each case by age, sex, and index year/month to create the control group. Cox's proportional hazard regression model with hazard ratios (HRs) and 95% confidence intervals (CIs) was conducted to estimate the impact of CRC on the risk of mood disorders. Results: Patients with CRC exhibited a significantly higher risk of developing mood disorders (adjusted HR = 3.05, 95% CI = 2.89-3.20) compared with the control group. This phenomenon was also observed for each type of mood disorder (depression, bipolar disease and anxiety), as well as across different subgroups by patient characteristics. However, a follow-up time longer than 1 year was more likely to have significantly increased risks, and we unexpectedly found that some treatments in CRC patients tended to have a decreased risk of anxiety compared to their counterparts. Conclusion: The findings of this population-based cohort study suggest that patients with CRC are at a higher risk of mood disorders, especially when follow-up time is longer than 1 year, but various treatments may inversely affect this association.