© 2000 The Royal College of Psychiatrists
Correspondence |
Cognitive effects of antipsychotics in schizophrenia and relationship to quality of life
Krankenhaus Spandau, Department for Psychiatry and Psychotherapy, 13578 Berlin, Germany
In his overview on cognitive effects of antipsychotics in schizophrenia Sharma (1999) stresses a relationship between cognitive function in schizophrenia and quality of life as an outcome measure. I think that Sharma's use of the concept ‘quality of life’ has to be clarified to prevent a number of rather common biases. He quotes two studies that are said to support a relationship between cognitive function in schizophrenia and quality of life (Davidson & Keefe, 1995; Green, 1996). The term quality of life is not operationalised in the first study. In the second study, which is in fact an overview of other studies, it is reported by Heinrichs' Quality of Life Scale (Heinrichs et al, 1984). Like most other instruments which have been used to detect the effect of atypical neuroleptics on quality of life in schizophrenia (Priebe et al, 1999) the Quality of Life Scale (subtitled "An instrument for rating the schizophrenia deficit syndrome") assesses clinical judgements of negative symptoms of schizophrenia rather than subjective appraisals of quality of life made by the patient. As it seems reasonable to assume at least a moderate relationship of negative symptoms and cognitive functions in schizophrenia, it is not surprising that a relationship is found between cognitive functioning and quality of life when the quality of life measures seem to be confounded to a considerable extent by psychiatric symptomatology.
We think that it is necessary to make a distinction between quality of life as an evaluation criterion for illness-related phenomena (negative symptoms), and quality of life as a subjective assessment by the patient as a "subjective evaluation of oneself and one's social and material world" (Orley et al, 1998) - that is, subjective quality of life, not as a disease but as a generic concept. Since there are some studies that show that cognitive functioning in schizophrenia may predict social outcome, and since objective social outcome is moderately (although surprisingly weakly) associated with generic subjective quality of life, some association between cognitive functioning and subjective quality of life is conceivable, but has not yet been supported by empirical evidence.
In a validation study of a German short form of the Lancashire Quality of Life Profile (Kaiser et al, 1999), equivalent to the English short form of the instrument MANSA (see Priebe et al, 1999), we did not find any significant correlation between any of the categories of the Wisconsin Card Sorting Test (WCST; Heaton et al, 1993) (number of categories, perserverative errors and responses, etc.) and the mean value of all satisfactions ratings, satisfaction with life as a whole and with satisfaction with mental health in a carefully selected sample of out-patients with DSM-III-R schizophrenia (American Psychiatric Association, 1987; n=36; mean age=47 years; mean illness duration=19 years). Our conclusion so far is that whether or not subjective quality of life is related to cognitive deficits in schizophrenia (in attention or memory, besides deficits in executive functioning, which are seen on a variety of tasks, most notably the WCST) remains unclear and so far is only a hypothesis, although it is widespread as an advertising slogan for atypical antipsychotic medication.
REFERENCES
- American Psychiatric Association (1987) Diagnostic and Statistical Manual of Mental Disorders (3rd edn, revised) (DSM-III-R). Washington, DC: APA.
- Davidson, M. & Keefe, R. S. E. (1995) Cognitive impairment as a target for pharmacological treatment in schizophrenia. Schizophrenia Research, 17, 123 -129.[CrossRef][Medline]
- Green, M. F. (1996) What are the functional
consequences of neurocognitive deficits in schizophrenia? American
Journal of Psychiatry, 153, 321
-330.
[Abstract/Free Full Text] - Heaton, R. K., Chelune, G. J., Talley, J., et al (1993) Wisconsin Card Sorting Test Manual — Revised and Expanded. Odessa, FL: Psychological Assessment Resources.
- Heinrichs, D.W., Hanlon, T. E. & Carpenter, W.T. Jr (1984) The Quality of Life Scale: an instrument for rating the schizophrenia syndrome. Schizophrenia Bulletin, 10, 388 -398.
- Kaiser, W., Isermann, M., Hoffmann, K., et al (1999) A short assessment of subjective quality of life. Application and results of a short form of the Berliner Lebensqualitätsprofil (BELP-KF) (in German). Fortschritte der Neurologie und Psychiatrie, 67, 413 -425.
- Orley, J., Saxena, S. & Herman, H. (1998)
Quality of life and mental illness. Reflections from the perspective of
WHOQOL. British Journal of Psychiatry,
172, 291
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[Free Full Text] - Priebe, S., Oliver, J. P. J. & Kaiser, W. (eds) (1999) Quality of Life and Mental Health Care. Petersfield: Wrightson Biomedical.
- Sharma, T. (1999) Cognitive effects of conventional and atypical antipsychotics in schizophrenia. British Journal of Psychiatry, 174 (suppl. 38), 44-51.
Author's reply
Section of Cognitive Psychopharmacology, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF
I thank Dr Kaiser for drawing attention to the relationship between cognitive function and quality of life in schizophrenia. Dr Kaiser does not find any relationship with a single test that he uses to assess cognitive function (the WCST) and a German short form of the Lancashire Quality of Life Profile and thus goes on to suggest that there is no relationship. However, there is evidence that such a relationship does exist (Addington & Addington, 1999). Dr Kaiser feels that Heinrichs' Quality of Life Scale (QLS) is an assessment of clinical judgements of negative symptoms but a detailed look at the scale reveals that the four sub-scales of the QLS do indeed measure interpersonal relationships, instrumental role functioning and common objects and activities, among others. It is true that this is an interviewer rating scale and it would be better to have subjective ratings of quality of life. We have indeed carried out such a study and our (as yet unpublished) results show an association between quality of life, as measured by the Lancashire Quality of Life Profile that Dr Kaiser refers to, and measures of cognitive flexibility, verbal ability and verbal memory. Perhaps if Dr Kaiser had used more than one test to assess cognitive functioning in his patients, he may have found an association, as the WCST measures only one aspect of cognitive function. Meanwhile, his point of using subjective measures of quality of life is well taken.
REFERENCES
- Addington, J. & Addington, D. (1999) Neurocognitive and social functioning in schizophrenia. Schizophrenia Bulletin, 25, 173 -182.
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