From Scientific American:
In this study, Owen et al. used MRI to measure the volume of the hippocampus, a central structure of the limbic system that is involved in emotion as well as in memory formation. They evaluated the MRIs of 268 men and women aged 58 and over, who were originally recruited for the NeuroCognitive Outcomes of Depression in the Elderly study, but who also answered several questions regarding their religious beliefs and affiliation. The study by Owen et al. is unique in that it focuses specifically on religious individuals compared to non-religious individuals. This study also broke down these individuals into those who are born again or who have had life-changing religious experiences. The results showed significantly greater hippocampal atrophy in individuals reporting a life-changing religious experience.
Italics are mine. Heh.