Baseline household income is associated with severity and course of severe mental illness

Poverty is associated with the severity of common mental health disorders and increased physical comorbidities. However, its effects on severe mental illness (SMI), beyond increasing their incidence, are less understood, especially in low- and middle-income countries. We here examined the relationship between baseline household income and subsequent mental and physical health outcomes in a large cohort of individuals diagnosed with schizophrenia or bipolar disorder in Colombia.

Retrospective cohort and case-control study using electronic health records from over 5 million Colombians. We identified individuals diagnosed with schizophrenia or bipolar disorder and their baseline household income. Mental health outcomes included third-line antipsychotic treatments (clozapine or antipsychotic polypharmacy) and psychiatric hospitalizations. Physical outcomes included diagnoses of hypertension, type 2 diabetes, and HbA1c levels, compared with rates in individuals without SMI.

We included 12,216 (6,485 women) participants newly diagnosed with bipolar disorder or schizophrenia between 2019 and 2023. Compared to middle-income participants (between $700-1,750USD/month), patients on a low income (less than $700USD/month) were more likely to require third-line antipsychotic treatment (OR 1.84 [1.64, 2.08]) and psychiatric hospitalization (incidence rate ratio 1.30 [1.21, 1.41]). Low-income participants with SMI had hypertension and diabetes rates like middle-income participants without SMI who were 20 years older. However, the combined effect of SMI and low income together posed a less-than-additive risk. Lower income was associated with higher HbA1c levels in diabetes, while a diagnosis of SMI was associated with lower levels.

Low income at SMI onset is associated with worse mental and physical health outcomes.