Abstract
Shailesh Kumar, Division of Psychiatry, Auckland Medical School and Rees Tapsell, Waitemata Health, Auckland, New Zealand:
We refer to the paper by MacKirdie and Shepherd on Capgras syndrome [1]. The authors, from a small town in New Zealand, have described five cases of Capgras syndrome, three of which are Maori. On the basis of these case reports they suggest that Capgras syndrome may be more common in New Zealand Maori. They go on to speculate that this increased rate among Maori might be a result of genetic and cultural factors. They also discuss the association between Capgras syndrome and violence, the relevance of which, to these cases, is unclear. This article purports to describe a series of case reports, but the authors describe the demographics of their catchment area and hospital admissions in a manner that implies an epidemiological study.
Conclusions such as ‘Capgras syndrome is possibly more common in Maori of New Zealand’, should be made only as a result of well-designed, methodologically sound studies that have paid careful attention to sampling, measurement and analysis [2]. This was not the case in this study. The sampling method used, in which the first author ‘became aware’ of her cases, is subject to significant selection bias. The authors do not discuss other significant details of sampling, for example, how many patients were screened, how many patients were excluded. The population base from which the authors found their cases is not representative of New Zealand.
The measurement and analytical techniques used are also open to bias and speculation. Clinical details provided in the paper are scant, at best. The authors mention that organic factors are frequently associated with Capgras syndrome, but no details of how organicity was investigated, or excluded, are given. In one case (case four) the authors make the diagnosis of Capgras syndrome because of spiritual substitution (a deceased nephew replacing the spirit of the patient's son). This is in direct contrast to the traditional description of substitution by physical look-alikes in Capgras syndrome.
Messages, expressed or implied, that any given condition is common among the Maori population should not be given from such flawed studies. We object to such fallacious conclusions being drawn from a small series of case reports. They may further disadvantage Maori by reinforcing some of the misperceptions held by lay public and even professionals [3]. To discuss the association of this syndrome with violence among an already disadvantaged group, in such an irrelevant fashion is, in our view, irresponsible. Previous authors have reported Capgras syndrome in different cultures [4, 5] but have shown the courtesy to these cultures of not ascribing its causation to racial factors as MacKirdie and Sheppard have. The only message that should be given from this series of case reports, is that Capgras syndrome transgresses cultural boundaries.
It was a disappointment to us and to many of our colleagues to read such an article in our college Journal because it raises questions about the peer review and editorial processes. It was particularly disappointing to read this article given the current emphasis on evidence-based decision making and methodological rigour in research. One is left to wonder whether this article was reviewed by somebody with an understanding of the Maori culture and epidemiological methods when such wide-ranging conclusions were being drawn from a small series of case reports.