Severe Mental Illness Tied to Higher Risk for Physical Health Comorbidities

Compared with people without severe mental illness, people with schizophrenia or bipolar disorder are at an increased risk for physical and psychiatric multimorbidity, according to study results published in Lancet Psychiatry.

Researchers conducted a systematic review and meta-analysis to determine the prevalence of physical and psychiatric multimorbidity in patients with severe mental illness, as well as assess the likelihood of physical multimorbidity in patients with and without severe mental illness.

The researchers searched databases through February 2024 for observational studies measuring multimorbidity prevalence among adult populations diagnosed with either schizophrenia or bipolar disorder. Physical multimorbidity was defined as 2 or more physical health conditions, while psychiatric multimorbidity was defined as 3 or more psychiatric conditions. Outcomes of interest included absolute prevalence of physical and psychiatric multimorbidity in people with severe mental illness, as well as odds of physical multimorbidity among people with and without severe mental illness. Statistical analyses included random-effects meta-analysis, sensitivity analysis, and meta-regression analysis.

A total of 82 observational studies comprising 1,623,773 people with severe mental illness (schizophrenia, n=1,223,561; bipolar disorder, n=318,585) and 13,235,882 people without severe mental health illness were included in the final review. In terms of methodological quality, 21 studies were of low quality, 33 studies were of average quality, and 28 studies were of high quality.

Of the 82 total studies, 75 reported individual patient data (pooled severe mental illness population: mean age, 47.9; men, 63%).

The odds of physical multimorbidity were 2.40 times (95% CI, 1.57-3.65; k=11; P =.0009) greater in people with severe mental illness vs those without. When stratified by mean age, the odds were higher in younger (mean age, ≤40: odds ratio [OR], 3.99; 95% CI, 1.43-11.10; k=3) vs older populations (mean age, >40: OR, 1.55, 95% CI 0.96-2.51; k=5; between subgroup differences P =.0013).

After stratifying by diagnosis, the OR for the bipolar disorder-only comparison was 3.20 (95% CI, 1.65-6.22; k=5; P =.0082), while the schizophrenia-only comparison had an OR of 2.16 (95% CI, 1.30-3.60; k=9; P =.0082). A pooled OR of 2.76 (95% CI, 1.36-5.60; P =.016) was observed for the combined schizophrenia and bipolar disorder cohorts.

With regard to absolute prevalence in people with severe mental illness, meta-analysis of physical multimorbidity yielded a pooled prevalence of 25% (95% CI, 0.19-0.32; k=29). Physical multimorbidity was more prevalent in cohorts with bipolar (pooled value, 29%; 95% CI, 0.20-0.41, k=14) vs schizophrenia (pooled value, 25%; 95% CI, 0.19-0.32; k=22).

Meta-analysis of psychiatric multimorbidity among people with severe mental illness yielded a pooled prevalence of 14% (95% CI, 0.08-0.23; k=21). Psychiatric multimorbidity was more prevalent in cohorts with bipolar (pooled value, 22%; 95% CI, 0.13-0.34, k=14) vs schizophrenia (pooled value, 10%; 95% CI, 0.03-0.26; k=9). Study limitations included the inability to control for several key covariates, reduced generalizability of results, inconsistencies in ethnicity data, potential publication bias, and not involving people with relevant lived experiences in the design and authorship of the study.

“The high prevalence of multimorbidity shown here constitutes a call to action, highlighting the need for integrated health services that facilitate both physical and mental health care,” the researchers concluded.

Disclosure: Several study authors declared affiliations with biotech and pharmaceutical companies. Please see the original reference for a full list of author disclosures.