Total population-based study of the impact of substance use disorders on the overall survival of
psychiatric inpatients
Sammanfattning
Background: Patients with severe mental illness have a shortened lifespan, and substance use
disorder (SUD) is an especially important diagnosis in this respect. There have been no studies
comparing directly SUD to other diagnoses in a nationwide cohort. Aims: To directly compare
differences in mortality rates of psychiatric inpatients with a discharge diagnosis of SUD versus
other psychiatric diagnoses. Methods: A register-based study was made of all patients admitted to
psychiatric hospitals in Iceland between 1983 and 2007. Patients were grouped according to
discharge diagnoses. Survival with respect to SUD was compared using Cox-proportional hazard
ratio, excluding those with an organic mental disorder. Furthermore, the survival of patients with SUD
and co-morbid diagnoses was evaluated. Results: A total of 14,281 patients (over the age of 18
years) were admitted to a psychiatric hospital in Iceland during the study period, with a total of
156,356 years of follow-up. For both men and women, a diagnosis of SUD conferred similar mortality
as a diagnosis of schizophrenia without SUD, while individuals with a diagnosis of a mood disorder
or "other disorders" had significantly lower mortality than SUD. For men with SUD, a co-occurring
mental disorder was associated with an increased risk of dying, however, this was not found for
women. Conclusions: SUD was the psychiatric diagnosis that had the highest mortality rate among
psychiatric inpatients, in both men and women. An additional psychiatric diagnosis on a pre-existing
SUD diagnosis did increase the risk for men but not women.