http://www.scientificamerican.com/article/religious-experiences-shrink-part-of-brain/
The article, “Religious factors and hippocampal atrophy in late life,” by Amy Owen and colleagues at Duke Universityrepresents an important advance in our growing understanding of the relationship between the brain and religion. The study, published March 30 in PLoS One, showed greater atrophy in the hippocampus in individuals who identify with specific religious groups as well as those with no religious affiliation. It is a surprising result, given that many prior studies have shown religion to have potentially beneficial effects on brain function, anxiety, and depression.
A number of studies have evaluated the acute effects of religious practices, such as meditation and prayer, on the human brain. A smaller number of studies have evaluated the longer term effects of religion on the brain. Such studies, like the present one, have focused on differences in brain volume or brain function in those people heavily engaged in meditation or spiritual practices compared to those who are not. And an even fewer number of studies have explored the longitudinal effects of doing meditation or spiritual practices by evaluating subjects at two different time points.