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

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.