Increased relative risk of subsequent affective disorders in patients with a hospital diagnosis of obesity

Abstract

To investigate the risk of clinical affective disorders of patients who were hospitalized because of obesity in the study period 1 January 1977 to 31 December 1999. Using data from Danish hospital registers, three study cohorts were identified by their diagnoses at discharge from hospital: one cohort comprising all patients with a first hospital admission with an index diagnosis of obesity, and two control cohorts comprising all patients with a first hospital admission with an index diagnosis of osteoarthritis or of non-toxic goiter, respectively. Later admissions to psychiatric hospital wards with discharge diagnoses of affective disorders were used as outcome events. Rates of readmission were estimated using competing risks models in survival analyses. Age, sex, abuse, and calendar time were included as covariables in the analyses. A study sample of 165,425 patients discharged with an index diagnosis was identified. In total, 1081 events occurred in the observation period. An index diagnosis of obesity was associated with an increased risk of affective-disorders hospitalization when compared with patients with osteoarthritis (Rate ratio: 1.35 (95% CI: 1.09-1.67)) and tended to be associated with an increased risk when compared to patients with non-toxic goiter (Rate ratio: 1.23 (95% CI: 0.99-1.53)). Patients with obesity diagnoses who did not have additional hospital diagnoses of substance- or alcohol abuse had a risk of affective disorders that was 1.55 (95% CI: 1.23-1.95) times greater than that of osteoarthritis patients without abuse diagnoses. Patients hospitalized with obesity may be prone to developing affective disorders that require in-hospital treatment, but the excess risk is modest. Severe obesity seems to be associated with other risk factors for mood disorders than those related to comorbid alcohol- or substance abuse.