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Cognitive Improvements in Test Linked to Practice Effects

Study finds only small improvements in schizophrenics' cognition from medications

MONDAY, Oct. 15 (HealthDay News) -- Schizophrenics taking second-generation antipsychotic medications who demonstrate improvements on cognitive tests may be demonstrating practice effects from taking the tests on multiple occasions, according to research in the October issue of the Archives of General Psychiatry.

Terry E. Goldberg, Ph.D., of the Albert Einstein College of Medicine in Glen Oaks, N.Y., and colleagues analyzed data from 104 subjects with first-episode schizophrenia and 84 healthy controls. People with schizophrenia commonly have cognitive impairments, and previous research has indicated that second-generation antipsychotics can improve cognitive ability. Subjects took olanzapine or risperidone for 16 weeks and took a battery of cognitive assessments at baseline, 6 weeks, and 16 weeks.

Researchers found that the differential effects of medication on cognitive ability appeared to be small. The schizophrenia group demonstrated greater rates of change on only two out of 16 cognitive measures compared to the control group. Some of the improvements in the schizophrenia group may have been due to familiarity with the tests or other practice effects.

"[We] hope that our findings increase awareness of practice effects as a potential source of cognitive change in clinical trials and that our findings can be used heuristically in the development of study designs and tests that are relatively insensitive to practice-related changes. Such advances may be important for improving methods involved in the assessment of cognitive change in clinical trials," the authors wrote.

The authors reported either being employed or receiving financial support from pharmaceutical companies manufacturing medicines to treat schizophrenia.

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