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Are herbal medicines beneficial for treating symptoms of schizophrenia?
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Myeong Soo Lee, Research Fellow Complementary Medicine, Peninsula Medical School, Universities of Exeter & Plymouth, Exeter, UK
Send letter to journal:
drmslee{at}gmail.com Myeong Soo Lee
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Dear Editor I read with interest this systematic review in which the efficacy of herbal medicines for treating Schizophrenia were analyses (1). Although this review was performed rigorously in their methods, I disagree with the authors' conclusion where they suggested that 'combining Chinese herbal medicine with antipsychotics is beneficial' through pooling the data of seven randomised clinical trials (RCTs). It has some flaws in meta-analysis and limitation to conclude the effectiveness of these treatments. The authors did not consider heterogeneity of the included trials when they pooled the results of the studies that they used in their meta- analysis (1). The quantification of heterogeneity of data is only one component of a wider investigation of variability across studies, the most important being diversity in clinical and methodological factors (2). Generally, we consider statistical heterogeneity to be present when the chi-squared statistic is less than 0.10 and the I-squared statistic is greater than 50% (3). The authors employed a fixed effects model even though there is heterogeneity in types of interventions. Only two results of BPRS and leaving the study early in medium-term avoid the statistical heterogeneity according to Cochrane textbooks. Moreover, there is clinical heterogeneity according to type of herbs and control interventions. Three RCTs compared Gingko biloba combined with antipsychotics with placebo plus antipsychotics. The author said there was no evidence that this herb had remarkable effects. The results of the other three randomized clinical trials reported positive effects of herbs plus antipsychotics for treating Schizophrenia when compared with antipsychotics alone. However, these trials were designed as add-on intervention for antipsychotics. It is conceivable that with such a design, the experimental treatment will seem to be effective even if it is, in fact, a pure placebo: the nonspecific effects of these intervention are likely to generate a positive result even in the absence of specific effects of intervention (4). For these reasons, I am of the opinion that there is insufficient evidence to establish that herbs alone or plus antipsychotics are an effective treatment for treating Schizophrenia. More cautious analysis is required if sound conclusions are to be drawn from a meta-analysis of data that is highly heterogeneous. Competing interests None to declare References 1 Rathbone, J., Zhang, L., Zhang, M., et al (2007) Chinese herbal medicine for schizophrenia: cochrane systematic review of randomised trials. Br J Psychiatry, 190, 379-384. 2 Thompson, S. G. (2001) Why and how sources of heterogeneuty should be investigated. In Systematic reviews in health care (eds M. Egger, G. D. Smith & D. G. Altman), pp. 157-175. London: BMJ Publishing. 3 Higgins, J. P. T., Greens, S. & editors (2006) Cochrane handbook for systematic reviews of interventions 4.2.6 [updated September 2006]. In Cochrane Library, Issue 4, 2006. Chichester, UK: John Wiley & Sons, Ltd. 4 Ernst, E. (2007) Placebo, deceit and complementary/alternative medicine. Climacteric, 10, 85-87. |
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