According to this study, divorce rates weren’t lower for religious people — unless they attended services:
Frequency of divorce and separation among 15,714 adults from the British Social Attitudes data set for 1985-2005 peaked at around 50 years of age, and increased significantly over the period of study. Ratios of marital breakdown were compared between those of no religious affiliation and Christian affiliates with different levels of church attendance.
Frequent Christian attendees were 1.5 times less likely to suffer marital breakdown than nonaffiliates, but there was no difference between nonattending Christian affiliates and those of no religion. Infrequent Christian attendees were 1.3 times less likely to suffer marital breakdown compared to nonaffiliates, suggesting that even infrequent church attendance might have some significance for predicting the persistence of marital solidarity.
Source: “Does Religion Make a Difference? Assessing the Effects of Christian Affiliation and Practice on Marital Solidarity and Divorce in Britain, 1985–2005″ from Journal of Divorce & Remarriage, Volume 51, Issue 6, 2010