It was an interesting study but it was criticized in the scientific community. Well, he did another study in 2009 and this time was more rigorous. The follow up study is called The Chronic Dependence of Popular Religiosity upon Dysfunctional Psychosociological Conditions. Now I haven't read the whole thing, but Tom Rees of Epiphenom has. He was attracted to the charts, as I was, which I've added below.
What societal ills bring a country down from being successful and healthy? Paul used indicators like murder, suicide rates, size of prison populations, mortality, alcohol consumption, poverty, unemployment, sexually transmitted diseases, abortions and deaths. I think he had some positive indicators like marriages too.
Results? Unhealthy societies are more religious. Religion needs a dysfunctional society to flourish, which explains why a first world country like the U.S. can still be so religious, as you can see in all the charts. (click for larger versions)
