Across 85 countries around the world, Voracek (2004) found a significant positive relation between estimated national intelligence (IQ) and national male and female suicide rate. The relation was not attenuated when countries’ per capita Gross Domestic Product (GDP) and type of national IQ estimation were statistically controlled. Independently, investigating the total national suicide rate only, Lester (2003) arrived at the same conclusion. These two findings are consistent with a corollary of de Catanzaro’s (1981) evolutionary theory of human suicide, namely that a threshold intelligence is necessary for suicidality and that intelligence and suicide mortality should thus be positively related. Here, further evidence for this hypothesis is bolstered by focusing on suicide rates of the elderly. Across 48 Eurasian countries, estimated national IQ was significantly positively related to national suicide rates of people aged 65 years and over. This new ecological-level finding survived statistical controlling for a set of seven variables (type of national IQ estimation, national GDP, stableness and recency measures for suicide rates, and rates of adult literacy, urbanization and Roman Catholics), which thus are not confounding factors for the relation of intelligence and suicide mortality. Based on ecological data, the threshold IQ for suicidality is predicted to be 70 or slightly over, an estimate that is consistent with various suicidological observations.
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