Contribution of psychiatric illness and substance abuse to 30-day readmission risk.

BACKGROUND: Little is known about the contribution of psychiatric illness to medical 30-day readmission risk.
OBJECTIVE: To determine the independent contribution of psychiatric illness and substance abuse to all-cause and potentially avoidable 30-day readmissions in medical patients.
DESIGN: Retrospective cohort study.
SETTING: Patients discharged from the medicine services at a large teaching hospital from July 1, 2009 to June 30, 2010. MEASUREMENTS: The main outcome of interest was 30-day all-cause and potentially avoidable readmissions; the latter determined by a validated algorithm (SQLape) in both bivariate and multivariate analysis. Readmissions were captured at 3 hospitals where the majority of these patients are readmitted.
RESULTS: Of 6987 discharged patients, 1260 were readmitted within 30 days (18.0%); 388 readmissions were potentially avoidable (5.6%). In multivariate analysis, 2 or more prescribed outpatient psychiatric medications (odds ratio [OR]: 1.1, 95% confidence interval [CI]: 1.01-1.20) or any prescription of anxiolytics (OR: 1.16, 95% CI: 1.00-1.35) were associated with increased all-cause readmissions, whereas discharge diagnoses of anxiety (OR: 0.82, 95% CI: 0.68-0.99) or substance abuse (OR: 0.80, 96% CI: 0.65-0.99) were associated with fewer all-cause readmissions. These findings were not replicated as predictors of potentially avoidable readmissions; rather, patients with discharge diagnoses of depression (OR: 1.49, 95% CI: 1.09-2.04) and schizophrenia (OR: 2.63, 95% CI: 1.13-6.13) were at highest risk.
CONCLUSIONS: Our data suggest that patients treated during a hospitalization for depression and for schizophrenia are at higher risk for potentially avoidable 30-day readmissions, whereas those prescribed more psychiatric medications as outpatients are at increased risk for all-cause readmissions. These populations may represent fruitful targets for interventions to reduce readmission risk.