How does severe mental illness impact on cancer outcomes in individuals with severe mental illness and cancer? A scoping review of the literature.

Introduction: Individuals living with severe mental illness (SMI) have a reduced life expectancy of approximately 15-20 years compared to the general population. Individuals with SMI and comorbid cancer have increased cancer related mortality rates compared to the non SMI population. This scoping review examines the current evidence in relation to the impact on cancer outcomes where individuals have a pre-existing SMI.

Methods: Scopus, PsychINFO, PubMed, PsycArticles and the Cochrane Library were searched for peer reviewed research articles, published in English language between 2001 and 2021. Initial title and abstract screening, followed by full text screening sourced articles reporting on the impact of SMI and cancer on: stage at diagnosis, survival, treatment access or quality of life. Articles were quality appraised, and data were extracted and summarised.

Results: The search yielded 1226 articles, 27 met the inclusion criteria. The search yielded no articles that met the inclusion criteria that were from the perspective of the service user or that were focused on the impact of SMI and cancer quality of life. Three themes were developed following analysis: Cancer related mortality, stage at diagnosis, and access to stage appropriate treatment.

Discussion: The collective study of populations with comorbid SMI and cancer is complex and challenging without a large-scale cohort study. The studies yielded through this scoping review were heterogenous and often study multiple diagnoses of SMI and cancer. Collectively these indicate that cancer related mortality is increased in the population of individuals with pre-existing SMI and the SMI population are more likely to have an increased likelihood of metastatic disease at diagnosis and less likely to receive stage appropriate treatment.

Conclusions: Individuals with pre-existing SMI and cancer have increased cancer specific mortality. Comorbid SMI and cancer is complex, and individuals with SMI and cancer are less likely to receive optimal treatments, experience increased interruptions and delays to treatment.