The methodological and conceptual aspects of mortality studies in psychiatry

Excess mortality in people with mental illness: findings from a Northern Italy psychiatric case register

PURPOSE

People with mental disorders show mortality rates up to 22.2 times higher than that of the general population. In spite of progressive increase in life expectancy observed in the general population, the mortality gap of people suffering from mental health problems has gradually widened. The aim of this paper was to study mortality rates in people suffering from mental illness in a cohort of people (16,981 subjects) in the local mental health register of the province of Modena during the decade 2006-2015.

METHODS

Standardized Mortality Ratios (SMRs) were calculated to compare the mortality of people with mental disorders to the mortality of people living in the province of Modena and the excess of mortality was studied in relation to the following variables: gender, age group, diagnosis and causes of death. In addition, Poisson regression analysis was performed to study the association between patient characteristics and mortality.

RESULTS

An overall excess mortality of 80% was found in subjects under the care of mental health services as compared to the reference population (SMR = 1.8, 95% CI 1.7-1.9). Subjects in the 15-44 year group presented the highest SMR (9.2, 95% CI 6.9-11.4). The most prevalent cause of death was cancer (28.1% of deaths). At the Poisson regression, the diagnosis "Substance abuse and dependence" showed the highest relative risk (RR) (4.00). Moreover, being male, single, unemployed and with a lower qualification was associated with higher RRs.

CONCLUSIONS

Our study confirms that subjects with mental illness have higher SMR. Noteworthy, the overall higher risk of mortality was observed in the younger age group.

Mortality among people with mental disorders

Mortality among psychiatric patients has been found to be higher than the general population, not only in those long-term residents in old-fashioned psychiatric hospitals or attending hospital-based psychiatric services (Harris & Barraclough, 1998) but also in those treated in modern community-based systems of care (Amaddeo et al., 1995; Grigoletti et al., 2009).