What is measured by verbal fluency tests in schizophrenia?
BACKGROUND
Schizophrenia patients perform below the norm on verbal fluency tests. The causes for this are unknown, but defective memory, executive functioning and psychomotor speed may play a role.


METHODS
We examined 50 patients with schizophrenia and related disorders, and 25 healthy controls with a cognitive test battery containing tests for verbal memory, executive functioning and psychomotor speed, and a categorical fluency test.


RESULTS
Patients obtained significantly lower test results than the controls on most cognitive measures including the verbal fluency test. During the fluency test, they formed as many clusters, and switched as often between clusters as the controls did, but they generated fewer words per cluster. Interestingly, in the control group, fluency performance was predicted by memory and executive functioning, but not by psychomotor speed. In patients, verbal fluency was predicted by psychomotor speed, but not by memory or executive functioning.


CONCLUSIONS
We conclude that psychomotor speed could be a crucial factor in cognition, and its influence on cognitive test performance should be considered in schizophrenia research. Furthermore, these data illustrate the importance of qualitative analysis of cognitive impairments in schizophrenia patients, as traditional cognitive tests often only provide quantitative information.
Department of Psychotic Disorders, P.O. Box 3007, GGZ-Drenthe, Assen 9400 RA, The Netherlands. m.van.beilen@neuro.azg.nl
Marije
M
van Beilen
Marieke
M
Pijnenborg
Ed H
EH
van Zomeren
Robert J
RJ
van den Bosch
Frederiec K
FK
Withaar
Anke
A
Bouma
D000328:Adult; D003071:Cognition / Q000502:physiology; D005260:Female; D006801:Humans; D007807:Language Tests; D008297:Male; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011340:Problem Solving / Q000502:physiology; D011597:Psychomotor Performance / Q000502:physiology; D012559:Schizophrenia / Q000503:physiopathology*; D013064:Speech Disorders / Q000209:etiology*; D014705:Verbal Behavior / Q000502:physiology*; D014706:Verbal Learning / Q000502:physiology