A Finnish study published in JAMA Psychiatry found a robust but temporally varying negative income gradient in first hospital-treated mental disorders. Patients admitted for the first time to psychiatric inpatient care were often from low-income households.

Kimmo Suokas, MD, of the Faculty of Social Sciences, Tampere University, in Finland, and colleagues used data from the nationwide Finnish Hospital Discharge and Statistics registry and population registers to determine annual incidence rates of first psychiatric hospital admission from 1996 through 2014. As a result, the entire population of Finland (N=6,258,033) was included in the study.

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A total of 186,082 first psychiatric inpatient treatment episodes occurred with incidence rates per 1000 person-years ranging from 1.59 in 2014 to 2.11 in 2008. Men constituted 50.2% of the patients, and the incidence rate was higher in males at the beginning of the study. In contrast, the incidence rate was higher in women at the end of the study.

Statistically significant increases did not occur in any of the 4 most common psychiatric diagnoses in men or women in the highest income decile; however, they occurred in all diagnostic categories in the lowest income decile with the exception of neurotic, stress-related, and somatoform disorders in men.

After adjusting for potential confounders, including education level, urbanicity, living alone, and decrease in income in the prior 3 years, the negative income gradient in the incidence rates for first hospital admissions for mental disorders among adults remained. The incidence risk ratio for adults varied from 2.94 in the lowest compared with 4.46 in the highest income decile. The highest incidence risk ratio for adults in the lowest income decile were observed 1 year (3.68), 3 years (2.97), and 5 years (2.71) before first admission. Notably, the negative income gradient was steepest for schizophrenia, psychotic disorders, and substance use disorders.

The investigators noted that “this finding is in line with the psychosocial theory of health inequalities, which states that adversity and stress associated with lower income increase the risk of a variety of illnesses, although the mechanisms linking income and mental health vary between disorders.”

The study was limited by its inability to obtain comprehensive data on outpatient treatments before the first hospitalization, the failure to account for all monetary income, and the difficulty of capturing wealth or determining causality in health inequality.

In an editorial accompanying the article, Vikram Patel, PhD, of the department of global health and social medicine, Harvard Medical School in Boston, Massachusetts, called for population level interventions aimed at reducing social distance. He also advocated for targeted interventions for low-income populations to reduce stressors associated with economic insecurity and improve access to community-based mental health care.

Dr. Patel wrote, “One thing is certain: being poor is harmful for one’s mental health, no matter how rich or happy the country where you live.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

References

  1. Suokas K, Koivisto A-M, Hakulinen C, et al. Association of income with the incidence rates of first psychiatric hospital admissions in Finland, 1996-2014 [published online December 18, 2019]. JAMA Psychiatry.doi:10.1001/jamapsychiatry.2019.3647
  2. Patel V. Income inequality and psychiatric admission in a rich country: happiness does not guarantee mental health equity. JAMA Psychiatry. 2019. Doi:10.1001/jamapsychiatry.2019.