Psychosocial and Demographic Factors Associated with Physical Multimorbidity in Severe Mental Illness: A Systematic Review

Background and Hypothesis People with severe mental illness (SMI), such as schizophrenia and bipolar disorder have a reduced life expectancy. This is largely due to physical multimorbidity (MM), defined as the coexistence of two or more physical health conditions. This systematic review identifies which psychosocial and demographic factors are associated with MM in SMI. Study Design Embase, PubMed, and PsychINFO were searched with no limits on publication date or study design. Studies were eligible for inclusion if they assessed the impact of psychosocial and/or demographic factors on MM outcomes among people with SMI. Study Results Thirty studies met the inclusion criteria for this review. The strongest predictors of MM were childhood maltreatment (odds ratios [OR] up to 8.70 [95% CI 2.49-30.33]), female gender (OR up to 2.47 [95% CI 1.35-4.50]), older age (OR up to 1.60 [95% CI 1.31-1.96]), and ethnicity (e.g. OR up to 2.09 [95% CI 1.81-2.42] for Black Caribbean groups relative to White British groups). Predictors with mixed evidence included educational attainment, employment status, socioeconomic status, marital status, urbanicity, deprivation, country of origin, healthcare access, and global functioning. Conclusions The findings highlight psychosocial factors (e.g. childhood maltreatment) and demographic factors (e.g. older age) that may contribute to MM, which has strong clinical implications. Some factors are modifiable (e.g. education) and can inform risk prevention strategies for MM in SMI, mitigating risks of premature mortality. Future research should use consistent definitions of MM for cross-study comparisons and assess additional risk factors, their interactions, and underlying mechanisms.