Search

Background: The objective of this study was to assess the ecological association of dietary tryptophan intake and suicide rates across industrialized nations. Tryptophan, an essential amino acid, is the rate-limiting precursor of serotonin biosynthesis. The serotonergic system has been strongly implicated in the neurobiology of suicide.Methods: Contemporary male and female suicide rates for the general population (42 countries) and the elderly (38 countries) were correlated with national estimates of dietary tryptophan intake.Results: Measures of tryptophan intake were significantly negatively associated to national suicide rates. Controlling for national affluence, total alcohol consumption and happiness levels slightly attenuated these associations, but left all of them negative.Limitations: The effect is an ecological (group-level) finding. Estimated per capita tryptophan supply is only a proxy for actual consumption.Conclusions: Developed nations ranking high in dietary tryptophan intake rank low in suicide rates, independent of national wealth, alcohol intake and happiness. [ABSTRACT FROM AUTHOR]

Background: Suicide-epidemiological research on short-term effects of elections on national/regional suicide and parasuicide incidence has yielded contradictory evidence. Reversing the cause–effect relationship of this line of research we investigated whether preceding regional suicide rates are related to subsequent election results. Methods: For Austria’s 121 districts, we regressed averaged standardized suicide rates for the preceding period (1988–1994) on political parties’ subsequent electoral gains/losses (1999-to-1995) while controlling for a set of 12 domain-relevant psychosocial/economic indices. Results: Stepwise weighted multiple regression led to a significant model. The 1999-to-1995 electoral gains/losses of two opposition parties, together with the population variation caused by migration balance and by births/deaths balance, accounted for a substantial part (30%) of the variability in preceding district-level suicide rates. Various other social indices failed to contribute further substantial increments to this model. Conclusions: This finding suggests that variations in preceding regional suicide incidence might be mirrored in subsequent changes in voting behavior. A speculative post hoc explanation for the finding is offered: on a community level, suicide’s aftermath might produce socially and politically alienated survivors of suicide who co-shape swings towards opposition parties in subsequent general elections. The finding calls for more research on suicide’s long-term aftermath. Limitations: Within-country replicability and cross-national generalizability await further investigation. At present, the factor/mechanism accounting for this finding is neither well-established nor has been directly tested. [Copyright &y& Elsevier]