According to a new study by Theresa Wimberley, MSc, Henrik Støvring, PhD, Holger J Sørensen, PhD, Henriette T Horsdal, PhD, James H MacCabe, PhD, and Christiane Gasse, PhD, “Predictors of treatment resistance in patients with schizophrenia: a population-based cohort study,” published online February 24 in Lancet Psychiatry, treatment-resistant schizophrenia might be a distinct subtype of schizophrenia rather than merely a more severe form.

The study, funded by European Community’s Seventh Framework Programme, included thousands of patients, 21% of whom were classified as “treatment resistant”–either (a) needing early therapy clozapine (commonly used when other treatments fail), or (b) hospital admission for schizophrenia after two failed treatment attempts. The study found key factors related with treatment-resistant schizophrenia that were different from known risk factors for treatment-responsive schizophrenia, signaling the potential that they are separate disorders.

“These findings are consistent with the possibility that, rather than representing a severe form of schizophrenia, the treatment-resistant subtype could have a fundamentally different cause than the treatment-responsive subtype.”

The study does not draw a definite conclusion. An accompanying editorial by Mathias Zink, MD, and Susanne Englisch, MD (Central Institute of Mental Health, University of Heidelberg, Mannheim, Germany) acknowledges that the study identifies a possibility, but warns against jumping to conclusions.

“…more research involving comprehensive psychopathological examinations, neurogenetic profiling, and functional magnetic resonance imaging will be necessary to provide a sound basis for this hypothesis.”