Division of Psychological Medicine, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK
Marui
& Farmer (2001) adduce
selective evidence in support of the hypothesis of greater genetic influence
on suicide than has previously been considered. In advancing this idea, they
pay insufficient regard to national variations in a number of factors
potentially relevant to differences in suicide rates. Data on national
differences in the prevalence of psychiatric disorders surely an
important potential confounder are glaringly absent from the paper,
and cultural differences not appearing in conventional tables of
known risk factors, including patterns of alcohol consumption,
are also neglected.
At the level of population genetics,
Marui
&
Farmer make a crucial error in grouping Hungarians genetically with Finns:
Finno-Ugrian is a language family, not an ethnic one; and although both
Finnish and Hungarian populations contain comparable (although by no means
identical) proportions of non-European genes (see, for example,
Guglielmino et al,
1990), the Finnish population is highly unusual, enriched as it is
with certain rare hereditary disorders (see, for example,
Ranta et al, 2001).
Cavalli-Sforza (2000) suggests
that this is due to abnormal statistical fluctuations that arose in a very
small founding population. Unless
Maru
i
&
Farmer can suggest genes that might plausibly affect suicidal behaviour,
specific polymorphisms which are shared by different Finno-Ugrian-speaking
populations but not by less suicide-prone populations, then their grouping
together of these geographically separated nations appears, at best,
questionable. Accepting that there are true differences in suicide rates
between, say, Finnish and Swedish populations, it is sensible to consider
potential, unexamined cultural explanations. There are several from the
sociological literature, including the proposal that Finland has a more
anxious culture than Sweden (reflected in its significantly higher score on a
measure termed uncertainty avoidance;
Hofstede, 1991). Another is
differential social capital. Interestingly, in this regard, Swedish-speaking
Finns have a longer active life than Finnish-speaking Finns
(Hyyppa & Maki, 2001); the
authors interpret this as reflecting differences in social capital, and
certainly it illuminates the possibility that such differences might influence
propensity to suicide. There are other relevant comparisons. Estonia, for
example, is cited by the authors as having the third highest suicide rate in
Europe, in contrast to a relatively low rate in Sweden. The fact that Estonia
and Finland share a (Lutheran) faith with Sweden does not lead to the
conclusion that attitudes toward death and suicide are identical.
The purported black swan of Slovenia, matched with Mediterranean neighbours such as Italy on some psychosocial variables but with a higher suicide rate, is an interesting observation meriting further study. But there is another, non-genetic explanation for the difference: a 40-year history of separation. There is ample anecdotal evidence from the former USSR of decreasing confidence, selfesteem and standards of health after the fall of communism.
By emphasising the likely interaction of environmental and genetic
influences on suicide,
Marui
&
Farmer implicitly recognise that suicide is a complex and
emergent trait, yet they make too much of the implications for
suicide prevention of genetic research into suicide. I would argue that a more
realistic target for future genetic research in this field might be the
detection of genetic influences on various measures of impulsive behaviour,
including some forms of suicide, as a means to guide biological research into
impulsivity itself a mercurial construct that probably has complex
associations with clinical outcomes.
REFERENCES
Cavalli-Sforza, L. L. (2000) Genes, Peoples and Languages (transl. M. Seielstad). London: Allen Lane.
Guglielmino, C. R., Piazza, A., Menozzi, P., et al (1990) Uralic genes in Europe. American Journal of Physical Anthropology, 83, 57-68.[Medline]
Hofstede, G. (1991) Cultures and Organizations: Software of the Mind. London: McGraw-Hill International.
Hyyppa, M. T. & Maki, J. (2001) Why do
Swedish-speaking Finns have longer active life? An area for social capital
research. Health Promotion International,
16, 55-64.
Marui
,
A. & Farmer, A. (2001) Genetic risk factors as possible
causes of the variation in European suicide rates. British Journal
of Psychiatry, 179,
194-196.
Ranta, S., Savukoski, M., Santavuori, P., et al (2001) Studies of homogenous populations: CLN5 and CLN8. Advances in Genetics, 45, 123-140.[Medline]
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