Background
Receiving a cancer diagnosis is strongly associated with a higher risk of suicide. However, studies examining suicidality in patients with colorectal cancer show some inconsistencies, particularly concerning factors such as disease stage or specific diagnosis.
Methods
We conducted a systematic review and meta-analysis to investigate the association between colorectal cancer and suicide or suicidal ideation. EMBASE, MEDLINE, PsycINFO, Science Citation Index Expanded & Social Sciences Citation Index, CINAHL, and Google Scholar were searched from database inception to May 31, 2025. Eligible studies included longitudinal cohort or case–control designs involving patients with colorectal cancer aged ≥14 years. Control groups comprised individuals from the same population without cancer. Data were independently extracted by two researchers from published reports available in English or German. The primary outcome was suicide, defined as death from intentional self-harm; the secondary outcome was suicidal ideation, defined as non-fatal thoughts of suicide. We performed random-effects meta-analyses, assessing heterogeneity with Q and I2 statistics and publication bias with funnel plots, Begg's, and Egger's tests. The study was registered (PROSPERO: CRD420251051277).
Findings
Among 4,700 records screened, 44 studies met the inclusion criteria, encompassing at least 9,385,472 patients with colorectal cancer and 13,308 suicides. Of these, 34 studies reported Standardised Mortality Ratios (SMR; colorectal cancer patients: n = 8,251,924; suicides: n = 12,081) and were included in the meta-analysis. After excluding studies with potential overlap in patient populations, the primary analysis was based on nine independent studies including at least 1,204,072 individuals with colorectal cancer, of whom 2,731 died by suicide. For suicidal ideation, we report the results of five individual studies. All included studies met methodological quality criteria, with a Newcastle–Ottawa Scale score of ≥7. The findings indicate a significantly increased suicide risk for patients with colorectal cancer, with a pooled SMR of 1.40 (95% CI: 1.33–1.49, I2 = 28.17%, no evidence for publication bias) compared to the general population. Subgroup analyses revealed notably higher suicide risks among patients with metastatic disease (SMR = 3.63, 95% CI: 2.99–4.41), those under 40 years of age (SMR = 2.15, 95% CI: 1.60–2.88), and individuals diagnosed within the past six months (SMR = 2.69, 95% CI: 1.29–5.61). For suicidal ideation, primary studies did not observe differences between patients with colorectal cancer and their reference groups, such as cancer-free individuals (SMR = 1.70, 95% CI: 0.65–4.42) or patients with hepatic cancer (SMR = 1.14, 95% CI: 0.94–1.38).
Interpretation
Our results indicate the need for comprehensive psychological screening in patients with colorectal cancer, who show a substantially higher suicide risk than the general population. Particular attention should be given to vulnerable subgroups, including those with metastatic disease, younger patients, and those recently diagnosed. Implementing these results into clinical practice can help facilitate patient-centred, cost-effective psycho-oncological care. Notably, evidence from low- and middle-income countries remains scarce, and younger populations might be underrepresented, indicating that our results should be interpreted with caution for these groups.