Cancer in Severe Mental Illness Patients: A Retrospective Study.

Objective: Severe mental illness (SMI), including schizophrenia, bipolar disorder or depression, constitute a risk factor for premature death. SMI patients die more frequently and earlier of cancer than the general population. Chronic inflammation, lack of cancer screening and substance abuse could explain these premature deaths in SMI patients. The role of SMI in cancer incidence remains uncertain. This study aims to identify the temporal occurrence between SMI and cancer in the case of dual pathology, and to investigate possible associations between specific diagnoses of SMI and cancer locations.

Methods: We retrieved medical data on more than 2000 SMI patients in care in 2022 with follow-up for up to 54 years and searched for cancer diagnoses and addictive comorbidities.

Results: Most SMI patients with cancer had been diagnosed with SMI prior to cancer (85.8%). The most represented cancer was breast cancer (27.2%) followed by cutaneous cancer (16.6%) and prostate cancer (10.6%). No associations were found between pre-existing SMI and cancer diagnoses as a whole. No associations were found when considering specific psychiatric diagnoses of SMI and precise cancer locations. Psychoactive substance consumption was similar among the different SMI pathologies and were not associated with specific cancer except for alcohol and breast cancer as well as tobacco and lung cancer.

Conclusion: This study highlights the need to reconsider the complex interaction between SMI and cancer, including their temporal relationship and mutual impact. The link between specific psychiatric diagnoses and cancers should be investigated in larger studies cross-referencing psychiatric files and cancer-specific database.