Over at Live Science, the staff reports a recent study finding that people who left a “strict” religious group — i.e., Jehovah’s Witnesses and Mormons — tended to experience health declines after leaving the group. The key to this study is “strict,” as in a religious group that works hard and promulgates rules to regulate everyday aspects of life, including what a person eats and drinks.
There is of course the possibility that observed health declines have something to do with leaving the group, which is an especially difficult thing to do for people who were indoctrinated into a particular religion as a child:
The social bonds of belonging to the group might be another factor for better health. “The social solidarity and social support could have psychological benefits,” Scheitle said. Beside losing connection to these health benefits, exiting a religious group may increase stressful situations. “You could lose your friends or your family becomes upset when you leave, leading to psychological stress and negative health outcomes,” Scheitle said.
The study in question was done by Christopher Scheitle at Penn State and can be found in the current issue of Journal of Health and Social Behavior. Unfortunately, I have yet to see a study which asks whether belonging to a religious group can have negative health impacts. I can imagine a few such groups where this hypothesis might hold.