Association between antipsychotic/antidepressant drug treatments and hospital admissions in schizophrenia assessed using a mental health case register

Abstract

BACKGROUND: The impact of psychotropic drug choice upon admissions for schizophrenia is not well understood. AIMS: To examine the association between antipsychotic/antidepressant use and time in hospital for patients with schizophrenia. METHODS: We conducted an observational study, using 8 years' admission records and electronically generated drug histories from an institution providing secondary mental health care in Cambridgeshire, UK, covering the period 2005-2012 inclusive. Patients with a coded ICD-10 diagnosis of schizophrenia were selected. The primary outcome measure was the time spent as an inpatient in a psychiatric unit. Antipsychotic and antidepressant drugs used by at least 5% of patients overall were examined for associations with admissions. Periods before and after drug commencement were compared for patients having pre-drug admissions, in mirror-image analyses correcting for overall admission rates. Drug use in one 6-month calendar period was used to predict admissions in the next period, across all patients, in a regression analysis accounting for the effects of all other drugs studied and for time. RESULTS: In mirror-image analyses, sulpiride, aripiprazole, clozapine, and olanzapine were associated with fewer subsequent admission days. In regression analyses, sulpiride, mirtazapine, venlafaxine, and clozapine-aripiprazole and clozapine-amisulpride combinations were associated with fewer subsequent admission days. CONCLUSIONS: Use of these drugs was associated with fewer days in hospital. Causation is not implied and these findings require confirmation by randomized controlled trials.