Norms matter: U.S. normative data under-estimate cognitive deficits in Norwegians with schizophrenia spectrum disorders

Abstract

Objective: To illustrate and quantify how using different normative systems influences the accuracy of identifying cognitive impairment in people with schizophrenia spectrum disorders.

Participants and methods: A convenience sample of 315 patients between 18 and 38 years of age referred for neuropsychological assessment at a psychiatric inpatient hospital in Bergen, Norway, was included. All completed the Norwegian version of the Repeatable Battery for the Assessment of Neuropsy-chological Status (RBANS).

Results: There were statistically significant differences between the Immediate Memory, Visuospatial/Constructional, Language, Delayed Memory, and Total Scale Index scores when comparing the U.S. normative scores with the Scandinavian normative scores. The effect sizes were medium. The patient samples scored higher when using the U.S. normative data, suggesting less cognitive impairment.

Conclusions: United States normative data yielded less impaired scores for Norwegians with schizophrenia spectrum disorders. The implications of using U.S. versus Scandinavian normative data are discussed.