Genetic risk factors and variation in European suicide rates

Marus̆ic̆ & 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, Marus̆ic̆ & 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 Marus̆ic̆ & 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, Marus̆ic̆ & 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.