Severe Mental Illness Diagnosis and Temporal Chronic Physical Comorbidity

Individuals with SMI face a greater risk for chronic physical health problems that vary with SMI subtype and by time relative to the diagnosis of SMI.

Individuals with severe mental illness (SMI) face a greater risk for chronic physical health problems that vary with SMI subtype and by time relative to the diagnosis of SMI. At the point of diagnosis, individuals with psychotic illness have higher odds of more than 12 chronic conditions compared with a matched cohort without SMI. Among individuals with schizophrenia, odds are not as high in as many conditions, and are lower for multiple conditions suggesting these conditions are underdiagnosed in this population at the time of schizophrenia diagnosis. These are among the study findings published recently in Lancet Psychiatry.

A lack of understanding exists in the temporal relationship between a diagnosis of SMI and the onset of physical chronic disease, so researchers sought to evaluate the cumulative prevalence of 24 chronic physical conditions from 5 years before to 5 years after diagnosis of SMI.

They initiated a retrospective cohort study using the UK Clinical Practice Research Datalink (CPRD) to discover 68,789 patients aged 18 to 100 years diagnosed with SMI from January 2000 through December 2018. Each patient in the SMI cohort was then matched with up to 4 individuals (274,827 individuals in all in the CPRD) by sex, primary care practice, 5-year age band, and year of primary care practice registration who did not have SMI (cohorts combined median age, 40.90 years; IQR 29.46-56.00; 49.03% women).

Researchers set the primary endpoint as the cumulative prevalence of 24 chronic physical conditions at 1 year, 3 years, and 5 years before and after SMI diagnosis based on Charlson and Elixhauser comorbidity indices at the time of diagnosis. Regression analysis was used to compare patients in the SMI cohort and individuals in the matched cohort, adjusting for ethnicity, age, and sex.

Elevated odds of multiple conditions at the point of severe mental illness diagnosis suggest that early intervention on physical health parameters is necessary to reduce morbidity and premature mortality.

Participants were overwhelmingly White (87.03% SMI cohort, 88.99% matched cohort). Researchers found that at diagnosis, the most prevalent chronic conditions in the SMI cohort included asthma (15.38%), hypertension (12.64%), diabetes (7.12%), neurological disease (5.06%), and hyperthyroidism (4.17%). At the same time, patients diagnosed with schizophrenia were also diagnosed less frequently than matched controls in 9 of the 24 chronic conditions observed, and these patients also had increased odds compared with matched controls in 5 of the 24 chronic physical conditions.

They also discovered that patients with bipolar disorder and other psychoses faced increased odds in 15 of the 24 chronic conditions compared with matched controls at the time of SMI diagnosis. At 5 years following SMI diagnosis, all of these numbers increased to 13 of 24 chronic conditions for schizophrenia, 19 of 24 for bipolar disorder, and 16 of 24 for other psychoses.

Study limitations include possible delays in the recording of physical chronic health conditions in the CPRD, the preponderance of White participants limiting generalizability, and possible residual or unmeasured confounding.

Chronic physical health problems are a greater risk for individuals with SMI and those problems will vary according to SMI subtype and by time in relation to SMI diagnosis. At the point of SMI diagnosis, individuals with psychotic illness face greater odds of more than a dozen chronic conditions compared with the matched cohort. Researchers concluded that, “Elevated odds of multiple conditions at the point of severe mental illness diagnosis suggest that early intervention on physical health parameters is necessary to reduce morbidity and premature mortality.” They added that, “Some physical conditions might be under-recorded in patients with schizophrenia relative to patients with other severe mental illness subtypes.”

Disclosure: One study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

References:

Launders N, Kirsh L, Osborn DPJ, Hayes JF. The temporal relationship between severe mental illness diagnosis and chronic physical comorbidity: a UK primary care cohort study of disease burden over 10 years. Lancet Psychiatry. September 2022;9(9):725-735. doi:10.1016/S2215-0366(22)00225-5