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Neuroleptic drug effects on cognitive function in schizophrenia.
J M Cleghorn1, R D Kaplan, B Szechtman
1Department of Psychiatry, McMaster University, Faculty of Health Sciences, Hamilton, Ontario, Canada.
Schizophrenia Research
|May 1, 1990
Summary
Neuroleptic drugs impair cognitive functions like memory and motor skills in schizophrenia patients, suggesting these deficits aren't inherent to the illness itself. These findings impact understanding of schizophrenia's cognitive deficits.
Area of Science:
- Neuroscience
- Psychiatry
- Cognitive Psychology
Background:
- Schizophrenia is associated with cognitive impairments.
- The role of neuroleptic medication in these deficits is debated.
- Distinguishing medication effects from core illness symptoms is crucial.
Purpose of the Study:
- To compare neuropsychological performance in neuroleptic-treated, untreated schizophrenic patients, and healthy controls.
- To determine if observed cognitive deficits are attributable to neuroleptic medication or the schizophrenia illness itself.
- To investigate the impact of medication on specific cognitive domains.
Main Methods:
- Neuropsychological testing was administered to 37 neuroleptic-treated schizophrenic patients, 27 untreated schizophrenic patients, and 27 normal controls.
- Performance was assessed on tests of complex figure recall, maze planning, fine motor coordination, reaction time, and passage recall.
- Subgroup analyses included patients on benztropine and those with a history of substance abuse.
Main Results:
- Neuroleptic-treated patients showed poorer performance in complex figure recall, maze planning, and fine motor coordination compared to untreated patients.
- Controls and untreated patients performed similarly on these tasks, suggesting medication-induced deficits.
- Both patient groups exhibited slower, more variable reaction times and poorer paraphrased passage recall than controls, though neuroleptic treatment improved passage recall.
Conclusions:
- Cognitive impairments in complex figure recall, planning, and motor coordination are likely side effects of neuroleptic medication, not core features of schizophrenia.
- These medication-induced deficits resemble those seen in Parkinson's disease, linked to dopaminergic antagonism.
- The findings suggest that some cognitive deficits attributed to schizophrenia may be iatrogenic, necessitating careful consideration of medication effects.