Psychiatric and general medical conditions comorbid with schizophrenia in the national hospital discharge survey

Objective: Morbidity and mortality from general medical conditions are elevated among patients with schizophrenia compared with the general U.S. population. More than 50% of patients with schizophrenia have one or more comorbid psychiatric or general medical conditions. This study determined types of comorbid disorders and their prevalence among hospitalized patients with and without schizophrenia. Methods: Data from the National Hospital Discharge Survey, a nationally representative sample, were analyzed for 1979-2003 (N=5,733,781 discharges). For discharges of patients aged 15 to 64 with at least one comorbid condition, the conditions of those with a primary diagnosis of schizophrenia (N=26,279) were compared with those with other primary diagnoses (N=1,936,876). Proportional morbidity ratios (PMRs) were calculated. Results: The proportion of discharges listing schizophrenia, particularly schizoaffective disorder, increased significantly over time among both males and females. The proportion was higher among males, blacks, and discharges in the Northeast. Discharge records with a primary diagnosis of schizophrenia showed higher proportions of all comorbid psychiatric conditions examined and of some general medical conditions, including acquired hypothyroidism (PMR=2.9), contact dermatitis and other eczema (PMR=2.9), obesity (PMR=2.0), epilepsy (PMR= 2.0), viral hepatitis (PMR=1.4), diabetes type II (PMR=1.2), essential hypertension (PMR=1.2), and various chronic obstructive pulmonary diseases (PMR range 1.2-1.5). Conclusions: Knowledge of the risks of comorbid psychiatric and general medical conditions is critical both for clinicians and for patients with schizophrenia. Closer attention to prevention, early diagnosis, and treatment of comorbid conditions may decrease associated morbidity and mortality and improve prognosis among patients with schizophrenia.