View Full Version : IQ Differences and Suicide

James Brody
April 23rd, 2006, 01:16 PM
I stumbled over the following...

Tomassini later rebutted his observation about twin's IQ and cited their results with 21,000. (good gawd!). On the other hand, I think Segal's "Entwined Lives" notes a small but consistent drop in IQ with twins...

From another world, there are consistent data linking IQ with ancestry. And the distinguished George Howe Colt (November of the Soul: The Enigma of Suicide, Scribners, 2006) rambles at some length that Blacks, despite poverty and education problems, rarely kill themselves. Colt reaches no conclusions but, judging from the general tone of his book, would probably skip Voracek's data.

Also note: Catanzaro proposed, perhaps as early as 1981, that suicide is a product of inclusive fitness. Some of his data from '91 & '95 are summarized in Buss, Evolutionary Psychology, 2004. The business of a "threshold IQ" is new to me.


"BMJ 2003;327:1168 (15 November), doi:10.1136/bmj.327.7424.1168-a


"Risk of suicide in twins

"Intelligence of twins and singletons may explain risk

"EDITOR: Tomassini et al presented evidence for a lower suicide rate of twins compared with singletons.1 However, they did not present any data supporting their preferred explanative factor ("strong family ties") for this finding, and their explanation is therefore speculative. Other causal factors need to be considered. I give one example.

"According to de Catanzaro's evolutionary theory of human suicide, a threshold intelligence is necessary for suicidality.2 A corollary of this hypothesis is that human intelligence and suicide mortality should be positively related.

"This prediction has been confirmed in an ecological study of 85 countries.3 National intelligence is significantly positively related to the national suicide rate, and ethnic differences in intelligence correspond to ethnic differences in suicide rates. Furthermore, excess suicide prevalence has been observed in the highly gifted.3

"Following these convergent strands of evidence it would be expected that population subgroups with a lower intelligence level than the generality also show lower suicide mortality than the generality. It has long been known that mean scores in intelligence tests are some 6 IQ points (or 0.4 standard deviation units) lower for twins than for singletons.4 5 The current finding of Tomassini et al is consistent with the expectation that subgroups that are on average less intelligent than the general public also have a reduced suicide risk compared with the general public. It seems that the intelligence of twins needs to be considered as an explanatory factor for the current finding.

"Martin Voracek, research resident

"Department of Psychoanalysis and Psychotherapy, "Statistics and Documentation Branch, University of Vienna Medical School, A-1090 Vienna, Austria


"Tomassini C, Juel K, Holm NV, Skytthe A, Christensen K. Risk of suicide in twins: 51 year follow up study. BMJ 2003;327: 373-4. (16 August.)
de Catanzaro D. Suicide and self-damaging behavior: a sociobiological perspective. New York: Academic Press, 1981.
Voracek M. National intelligence and suicide rate: an ecological study of 85 countries. Pers Individ Dif (in press).
Record RG, McKeown T, Edwards JH. An investigation of the difference in measured intelligence between twins and single births. Ann Hum Genet 1970;34: 11-20.
Byrns R, Healy J. The intelligence of twins. J Genet Psychol 1936;49: 474-8. "

Fred H.
April 23rd, 2006, 03:24 PM
JimB: National intelligence is significantly positively related to the national suicide rate, and ethnic differences in intelligence correspond to ethnic differences in suicide rates.
However, there seems to be a negative correlation between IQ and mortality—from Wikipedia, http://en.wikipedia.org/wiki/IQ#Health_and_IQ :

Health and IQ—Persons with a higher IQ have generally lower adult morbidity and mortality. This may be because they better avoid injury and take better care of their own health, or alternatively may be due to a slight increased propensity for material wealth (see above). It also decreases the risk of Post-Traumatic Stress Disorder, severe depression, and schizophrenia. On the other hand, it increases the risk of Obsessive Compulsive Disorder [7].
Research in Scotland has shown that a 15-point lower IQ meant people had a fifth less chance of seeing their 76th birthday, while those with a 30-point disadvantage were 37% less likely than those with a higher IQ to live that long [8].
And here’s a little something to cheer up the atheists here (also from Wiki)—
Religiosity and IQ— Several studies have investigated the relationship between intelligence and the degree of religious belief, with most showing a negative correlation [6].

James Brody
April 30th, 2006, 03:50 PM

Thanks for the Wikki view but I lately suspect a bit of PC. Or Voracek is something of a bigot...

Anyway, I've found a way to rationalize too much IQ as a fitness problem...