"Use of sulpiride, mirtazapine, venlafaxine, and clozapine-aripiprazole and clozapine amisulpride combinations were associated with fewer subsequent admission-days in patients with schizophrenia," Dr. Rudolf N. Cardinal of the Behavioral and Clinical Neuroscience Institute, University of Cambridge, UK, said by email.
"These studies are correlative and do not prove causation," he cautioned.
Dr. Cardinal and colleagues analyzed eight years' of admission records at a secondary mental health care institution in Cambridgeshire. The analysis included nearly 1,500 patients with a diagnosis of schizophrenia and a median follow-up of five years.
In mirror-image analysis covering two years before and after therapy initiation, the researchers found treatment with amisulpride, aripiprazole, clozapine, fluoxetine, mirtazapine, olanzapine, quetiapine, and sulpiride was associated with fewer subsequent admissions in one year.
The association persisted in a "more stringent" two-year analysis for aripiprazole, clozapine, and sulpiride.
Using regression analysis, the researchers found a continued reduction in admissions with sulpiride and mirtazapine (estimated mean change, -20.4 and -11.6 days/year, respectively).
Treatment with clozapine-aripiprazole and clozapine-amisulpride combinations as well as venlafaxine was associated with significantly fewer hospitalized days (-17.7, -13.8, and -12.3 days/year, respectively).
Overall, the mean admission rate was 26.8 days/year.
"This analysis focused on patients with more severe disease, in that they had at least one hospital admission in the pre-drug period," the researchers note in the article online October 21 in NPJ Schizophrenia.
"Larger correlative studies are required to corroborate these effects, followed by randomized controlled trials if appropriate," Dr. Cardinal said. "We are all very keen that these are not misrepresented as causal-grade findings."
The authors reported no funding. One coauthor reported receiving research funding from Genus Pharmaceuticals and consulting fees from Roche/Genentech.