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Cognitive effects of olanzapine and clozapine treatment in chronic schizophrenia

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Abstract

Rationale

Schizophrenia patients are known to manifest widespread, multifaceted cognitive deficits. There is now an increasing emphasis on the critical importance of cognitive deficits for the functional outcome in schizophrenia. Typical antipsychotics, although effective in reducing positive symptoms of the illness, have not shown much effect on cognitive functions. Atypical antipsychotics have shown promise of improving some cognitive functions.

Objectives

This naturalistic study aimed to determine whether olanzapine and clozapine improve cognitive functioning in a sample of 48 patients with chronic schizophrenia who had either failed to show sufficient clinical improvements or suffered from distressing side effects with conventional antipsychotics and were switched to either olanzapine or clozapine for clinical reasons and, if so, whether the two drugs produce similar or different cognitive effects.

Methods

All patients completed a comprehensive battery of neuropsychological tests designed to index executive functioning, verbal learning, verbal and visual and memory, attention, working memory, and psychomotor speed at: (i) baseline, (ii) after 6 weeks and (iii) after 6 months of treatment with olanzapine or clozapine.

Results

From the initial 48 patients who remained on olanzapine (n=16) or clozapine (n=14) for the entire duration with continuous participation, 30 provided data for this study. There were improvements over time (i.e. from baseline through 6 weeks to 6 months) in both treatment groups on verbal fluency, verbal learning and verbal and visual memory measures.

Conclusions

The findings indicate similar beneficial effects of olanzapine and clozapine on verbal learning and memory measures in patients showing a favourable clinical response to these drugs.

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Acknowledgements

This study was supported by Novartis Pharmaceuticals, UK. Veena Kumari holds a Wellcome Trust Senior Fellowship in Basic Biomedical Science. We thank Mr. S. O'Neil and Ms. S. Drozd for their help in cognitive testing and Drs. M. Das and B. Binneman for help with clinical assessments of the patients.

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Authors and Affiliations

  1. Clinical Neuroscience Research Centre, 7 Twisleton Court, Priory Hill, Dartford, Kent, DA1 2EN, UK

    Tonmoy Sharma & William Soni

  2. Section of Cognitive Psychopharmacology, Institute of Psychiatry, King's College London, De Crespigny Park, London, SE5 8AF, UK

    Catherine Hughes & Veena Kumari

  3. Department of Psychology, Institute of Psychiatry, King's College London, De Crespigny Park, London, SE5 8AF, UK

    Veena Kumari

Authors
  1. Tonmoy Sharma
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  2. Catherine Hughes
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  3. William Soni
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  4. Veena Kumari
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Correspondence to Tonmoy Sharma.

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Sharma, T., Hughes, C., Soni, W. et al. Cognitive effects of olanzapine and clozapine treatment in chronic schizophrenia. Psychopharmacology 169, 398–403 (2003). https://doi.org/10.1007/s00213-003-1506-y

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  • DOI: https://doi.org/10.1007/s00213-003-1506-y

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