Association between recent cancer and suicide: Danish national cohort study

Background Being diagnosed with cancer can be stressful and has been linked to suicide. However, an updated analyses where a wide range of cancers are compared is lacking. Aims To examine whether individuals first-time diagnosed with cancer within the past 5 years had higher suicide rates than those with no such diagnosis. Associations with time since diagnosis, and stage and site of cancer, were analysed. Method A population-based cohort study design applied to nationwide, longitudinal data on all persons aged 15 years or above (N = 6 987 998) and living in Denmark between 2000 and 2021. Specific sites of cancer first-time diagnosed were considered as exposure for the subsequent 5 years, and death by suicide was examined as outcome. Adjusted incidence rate ratios (aIRRRs) were calculated using Poisson regression models and adjusted for sociodemographics, psychiatric disorders and suicide attempts prior to cancer diagnosis. Results In total, 707 513 (10%) individuals were included. While 12 800 individuals died by suicide in the non-cancer group, 601 died of suicide in the cancer group, resulting in an aIRR of 2.0 (95% CI: 1.9-2.1). The highest rate was found in the period immediately following diagnosis (<6 months: 3.9, 95% CI: 3.6-4.2 versus 4-5 years: 1.8, 95% CI: 1.5-2.0). Also, higher rates were found for high-stage tumours (3.1, 95% CI: 2.8-3.4). The highest aIRRs were found for pancreatic cancer (7.5, 95% CI: 5.8-9.7) and oesophageal cancer (7.1, 95% CI: 5.4-9.3). Almost all sites of cancer analysed showed elevated rates of suicide compared with individuals without cancer. Conclusions Several recently diagnosed cancers were linked to elevated rates of suicide, especially during the first period following diagnosis. High tumour stage was associated with the highest rates, as were cancer sites with poor prognosis, suggesting prioritisation of these patient groups for suicide prevention efforts.