I have been reviewing the
PDF of the study and I suspect there is more to it than at first meets the eye.
I suspect the effect he is describing is related to the origins of extreme evangelism for both Christian and Islamic society (and a few other less popular examples) and how they are potentially derivative of Evolutionary Psychology and the advantage of such warrior and evangelical survival memes (like the dependence on hope when all else fails) in harsh environments along with the potential advantages of an imposed (faith based memetics) placebo effect for primitive cultures.
A few hundred years ago rates of homicide were astronomical in Christian Europe and the American colonies (Beeghley; R. Lane). In all secular developing democracies a centuries long-term trend has seen homicide rates drop to historical lows (Figure 2). The especially low rates in the more Catholic European states are statistical noise due to yearly fluctuations incidental to this sample, and are not consistently present in other similar tabulations (Barcley and Tavares). Despite a significant decline from a recent peak in the 1980s (Rosenfeld), the U.S. is the only prosperous democracy that retains high homicide rates, making it a strong outlier in this regard (Beeghley; Doyle, 2000). Similarly, theistic Portugal also has rates of homicides well above the secular developing democracy norm. Mass student murders in schools are rare, and have subsided somewhat since the 1990s, but the U.S. has experienced many more (National School Safety Center) than all the secular developing democracies combined. Other prosperous democracies do not significantly exceed the U.S. in rates of nonviolent and in non-lethal violent crime (Beeghley; Farrington and Langan; Neapoletan), and are often lower in this regard. The United States exhibits typical rates of youth suicide (WHO), which show little if any correlation with theistic factors in the prosperous democracies (Figure 3). The positive correlation between pro-theistic factors and juvenile mortality is remarkable, especially regarding absolute belief, and even prayer (Figure 4). Life spans tend to decrease as rates of religiosity rise (Figure 5), especially as a function of absolute belief. Denmark is the only exception. Unlike questionable small-scale epidemiological studies by Harris et al. and Koenig and Larson, higher rates of religious affiliation, attendance, and prayer do not result in lower juvenile-adult mortality rates on a cross-national basis
Fig 4 relation of absolute belief to under five mortality
Fig5 Relation of belief to life expectancy
Legend for graphs
A = Australia
C = Canada
D = Denmark
E = Great Britain
F = France
G = Germany
H = Holland
I = Ireland
J = Japan
L = Switzerland
N = Norway
P = Portugal
R = Austria
S = Spain
T = Italy
U = United States
W = Sweden
Z = New Zealand