To Örebro University

Background: The diagnosis of cancer is strongly associated with the risk of mental disorders even in patients with no previous history of mental disorders. Accumulating data suggest that mental distress may accelerate tumor progression. We hypothesized therefore that mental disorders after a cancer diagnosis may increase the risk of cancer-specific mortality.

Patients and methods: We conducted a nationwide cohort study including 244 261 cancer patients diagnosed in Sweden during 2004-2009 and followed them through 2010. Through the Swedish Patient Register, we obtained clinical diagnoses of all mental disorders and focused on mood-, anxiety-, and substance abuse disorders (ICD10: F10-F16, F18-F19, F32-F33, F40-F41, and F43-45) that are commonly diagnosed among patients with cancer. We further classified the studied mental disorders into first-onset or recurrent mental disorders. We used Cox regression to estimate multivariable hazard ratios (HRs) with 95% confidence intervals (CIs) as a measure of the association between mental disorders after cancer diagnosis and cancer-specific mortality, adjusting for age, sex, calendar period, educational level, cancer stage, and cancer type at diagnosis.

Results: After cancer diagnosis, 11 457 patients were diagnosed with mood-, anxiety-, and substance abuse disorders; of which 7236 were first-onset mental disorders. Patients with a first-onset mental disorder were at increased risk of cancer-specific mortality (HR: 1.82, 95% CI: 1.71-1.92) while patients with a recurrent mental disorder had much lower risk elevation (HR: 1.14, 95% CI: 1.05-1.24). The increased cancer-specific mortality by first-onset mental disorders was observed for almost all cancer sites/groups and the association was stronger for localized cancers (HR: 2.00, 95% CI: 1.73-2.31) than for advanced cancers (HR: 1.49, 95% CI: 1.32-1.69).

Conclusions: Patients with a first-onset common mood-, anxiety-, or substance abuse disorder after cancer diagnosis may be at increased risk of cancer-specific death.