Effort and cognition in schizophrenia patients

Objective: The aim of this study was to determine whether low cognitive test scores in schizophrenia patients are due to insufficient effort and, if so, to what extent. Method: Mental effort was measured with the Word Memory Test (WMT), an effort test that has been extensively validated. Schizophrenic patients (n=64), non-psychotic psychiatric patients (n=63), neurological controls (n=20), and normal controls (n=44) were tested with a neuropsychological test battery measuring memory, attention and executive functioning. Results: The majority of the schizophrenia patients and a quarter of the psychiatric patients scored below the cut-offs for normal effort on the WMT. Scores on the effort test explained a significant amount of variance in the neuropsychological test performance of schizophrenic patients. This lends support to the notion that cognitive functioning in schizophrenia is compromised by insufficient effort. Furthermore, poor mental effort was related to negative symptoms. Conclusions: Poor mental effort might be considered a core symptom of schizophrenia, representing an executive, monitoring or motivational problem. Mental effort should be taken into consideration in the neuropsychological assessment of schizophrenic patients and of psychiatric patients in general. Controlling for this variable may have a considerable impact on research, assessment and treatment of cognitive disorders in schizophrenic patients. (c) 2005 Elsevier B.V. All rights reserved.