Background: This paper examines the potential impact of recruitment source differences in schizophrenia research by comparing the neuropsychological performance of volunteers from the NISAD Schizophrenia Research Register with recently published schizophrenia normative data for the Repeatable Battery for Neuropsychological Status (RBANS).
Methods: The Register sample comprised 285 volunteers with schizophrenia or schizoaffective disorder. Their RBANS performance was compared with US data from 575 predominantly outpatient-recruited schizophrenia patients.
Results: The Register sample displayed impairments in immediate and delayed memory, but near-normal language, attention and visuospatial-constructional performance (mean RBANS total score=88.72, SD=16.35). By contrast, health service-recruited schizophrenia patients displayed impairments on all RBANS scales (mean RBANS total score=70.54, SD=14.80). Within the Register sample, volunteers with low levels of current functioning had immediate and delayed memory performance comparable to the US schizophrenia sample. Gender and school completion status were also associated with different RBANS profiles.
Conclusions: These findings reinforce the notion that a severity/functioning gradient exists across schizophrenia recruitment sources, which has important implications for research design and generalizability. Memory impairments have emerged as a central feature of schizophrenia.