A PLoS One paper has just been published showing the religion, in particular religious experiences reported to be "life-changing", such as being "born" again, atrophies a part of your brain called the hippocampus, later in life. Religion does change your brain after all, and science can measure this effect. The article is free access, it can be read without a subscription. It is of course, technical, but I think it is fairly accessible to all. The study involves a fairly large number of subjects, >250 older adults, and hippocampal changes were measured using MRI. Atrophy of the hippocampus may have important clinical implications, since it has been identified as a marker of mental health problems such as depression and dementia, in older adults. Too early to draw any over-reaching conclusions such as "religions shrinks your brain and leads to mental illness in old people", but these findings certainly warrant further study, and raise a flag of caution.

Here is the abstract:

Religious Factors and Hippocampal Atrophy in Late Life

Amy D. Owen1, R. David Hayward2,3*, Harold G. Koenig1,2,4, David C. Steffens2,4, Martha E. Payne2,3

1 Center for the Study of Aging and Human Development, Duke University Medical Center, Durham, North Carolina, United States of America, 2 Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, North Carolina, United States of America, 3 Neuropsychiatric Imaging Research Laboratory, Duke University Medical Center, Durham, North Carolina, United States of America, 4 Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America

Abstract Despite a growing interest in the ways spiritual beliefs and practices are reflected in brain activity, there have been relatively few studies using neuroimaging data to assess potential relationships between religious factors and structural neuroanatomy. This study examined prospective relationships between religious factors and hippocampal volume change using high-resolution MRI data of a sample of 268 older adults. Religious factors assessed included life-changing religious experiences, spiritual practices, and religious group membership. Hippocampal volumes were analyzed using the GRID program, which is based on a manual point-counting method and allows for semi-automated determination of region of interest volumes. Significantly greater hippocampal atrophy was observed for participants reporting a life-changing religious experience. Significantly greater hippocampal atrophy was also observed from baseline to final assessment among born-again Protestants, Catholics, and those with no religious affiliation, compared with Protestants not identifying as born-again. These associations were not explained by psychosocial or demographic factors, or baseline cerebral volume. Hippocampal volume has been linked to clinical outcomes, such as depression, dementia, and Alzheimer's Disease. The findings of this study indicate that hippocampal atrophy in late life may be uniquely influenced by certain types of religious factors.

Citation: Owen AD, Hayward RD, Koenig HG, Steffens DC, Payne ME (2011) Religious Factors and Hippocampal Atrophy in Late Life. PLoS ONE 6(3): e17006. doi:10.1371/journal.pone.0017006