Dr Purdon and colleagues should be commended on their efforts to study
the highly important issue of long-term cognitive changes when patients with
schizophrenia are treated with different antipsychotic drugs.1
Their report raises many issues that we discuss in this letter.
In addition to assessing psychopathology, all patients were studied
using a neuropsychological test battery measuring cognitive functions in 6
domains (motor skills, attention, verbal fluency and reasoning, nonverbal
fluency and construction, executive skills, and immediate recall). From these
6 domains, the authors computed a general cognitive index. They conclude that
olanzapine has statistically significant advantages over both risperidone
and haloperidol in the general cognitive index. All statistically significant
differences between groups with regard to the 6 domains of cognitive functions
fell victim to an α correction for multiple testing. In a within-group
analysis, olanzapine showed significant advantages in only 1 of 6 specific
cognitive domains (immediate recall) and in 1 of 17 individual tests.
Weiss E, Kemmler G, Fleischhacker WW. Improvement of Cognitive Dysfunction After Treatment With Second-Generation Antipsychotics. Arch Gen Psychiatry. 2002;59(6):572-573. doi: