Are there inequities in the assessment or management of pain for people with severe mental illness living with life-threatening diseases? A mixed-methods systematic review.

Background: Pain relief is a fundamental human right, yet evidence suggests access to analgesia is not equitably distributed. People with severe mental illness (SMI) experience significant disparities in healthcare during life, which may also be mirrored at the end of life. This systematic review examines the extent of inequities and underlying factors contributing to disparities in pain care for people with SMI and life-threatening diseases. Methods: A mixed-methods systematic review of MEDLINE, EMBASE, AMED, CINAHL, PsycINFO and EThOS (January 2000-September 2024), hand-searching key journals and citation tracking. Two reviewers independently screened studies, and data were extracted using a standardised approach. A narrative synthesis was used to integrate findings. Results: Two thousand nine hundred seven records were identified, with eight studies meeting the inclusion criteria. Study quality ranged from 'very low' to 'high'. All quantitative studies were retrospective analyses of routine healthcare data, examining analgesic prescribing for people with schizophrenia. Despite variability in outcome measures, all studies found that individuals with schizophrenia received significantly less analgesia than those without SMI. Four qualitative studies explored clinicians' views on providing pain care to patients with SMI; only one study included patient experiences. Identified barriers to optimal pain management included patient-related factors (e.g. difficulties in pain expression, behavioural symptoms), clinician-related factors (e.g. diagnostic overshadowing, stigma) and systemic issues (e.g. fragmented care, restrictive prescribing practices). Conclusion: There is a striking lack of research on pain assessment and management for people with SMI and life-threatening illnesses, yet available evidence indicates clear inequities in care. These disparities may be driven by intersecting structural, social and clinical barriers, contributing to poorer end-of-life experiences. Addressing this gap requires urgent action from clinicians, policymakers and researchers. Future work should combine population-based studies to quantify prescribing disparities with qualitative research involving people with lived experience of SMI and their carers. Participatory, co-produced approaches are essential.