The impact of severe mental illness on lung cancer mortality of patients with lung cancer in Finland in 1990-2013: a register-based cohort study.

BACKGROUND

Although the link between severe mental illness (SMI) and elevated cancer mortality is well established, few studies have examined lung cancer survival and SMI in detail. Our study compared cancer-specific mortality in patients with lung cancer with and without a history of SMI and analysed whether mortality differences could be explained by cancer stage at presentation, comorbidity or differences in cancer treatment.

METHODS

We identified patients with their first lung cancer diagnosis in 1990-2013 from the Finnish Cancer Registry, their preceding hospital admissions due to SMI from the Hospital Discharge Register and deaths from the Causes of Death statistics. Competing risk analyses were used to estimate hazard ratios (HRs) for the impact of SMI on mortality.

RESULTS

Of the 37,852 lung cancer cases, 12% had a history of SMI. Cancer-specific mortality differences were found between patient groups in some cancer types after controlling for stage at representation and treatment. Men with a history of psychosis had excess mortality risk (HR = 1.24, 1.06-1.45) in squamous cell carcinoma. Similar excess risk was found among women with psychosis in small-cell carcinoma (HR = 1.76, 1.41-2.19) and in squamous cell carcinoma (HR = 1.67, 1.26-2.20) and among women with mood disorders in adenocarcinoma (HR = 1.37, 1.08-1.74). Patient group differences in HRs in five-year mortality did not markedly change from the 1990s.

CONCLUSIONS

We found elevated cancer-specific mortality among persons with a history of SMI. Collaboration between patients, mental healthcare professionals and oncological teams is needed to reduce the mortality gap between patients with cancer with and without SMI.