This interesting article http://www.cathnews.com/article.aspx?aeid=26508 discusses the possible relationship between the size of the hippocampus in older people based on their adherence to particular Christian denominations and sub-groups of those denominations.

As the sample size is quite tiny (268) it's possible that the differences are all illusory, but I thought it worthwhile to start a discussion. They also didn't include a control sample of Atheists, so as a non-born-again Protestant I might fancy my measurements against Catholics and charismatics, but have no idea whether my religious adherence is beneficial or not to my overall brain size.

And of course correlation doesn't equal causation.

Graham
The sample group of 268 people is not big enough to make conclusions about atrophy of the hippocampus.

There was a study about happiness on a recent TV documentary and religion was cited as playing a role for many older people as regards their general health and wellbeing suggesting religion should not be dismissed as a factor.

It would be easy to explain the correlation in terms of the rewarding and 'uplifting' experience that so many religious people find give their lives meaning, particularly those that feel they could not live without 'God'.

This article sites stress factors as relevant to the atrophy rate of the hippocampus.

http://www.nature.com/mp/journal/v2/n3/abs/4000254a.html

Perhaps that explains why born-again are not protected against the atrophy process (if one takes on board the religious affiliation correlation). If there has been some great stress or life-changing experience that leads one to take up religion later in life, it would fit with the stress correlation.

Some people manage stress better than others, and perhaps for many their religious faith acts as a buffer. I would imagine in that scenario hippies and alternate lifestylers might also do well or those less affected by social and economic pressures. Or those who find ways to deal with stress like meditation, healthy diet, exercise etc.

more info needed
we must remember the hippo is only part of the brain

strongly modified..
by things in the blood..

[like]
rem slep
http://en.wikipedia.org/wiki/Rapid_eye_movement_sleep

longterm memory
[hey that might explain trans-generational
[irrational]..blood fueds]
http://en.wikipedia.org/wiki/Long-term_memory

""During REM sleep high levels of acetylcholine
in the hippocampus suppress feedback....""

http://www.chacha.com/question/what-is-the-purpose-of-the-hippocampus

""The hippocampus is an area buried deep in the forebrain
that helps regulate emotion..and memory.

It is part of the olfactory cortex..

plasticity of the hippo
http://linkinghub.elsevier.com/retrieve/pii/S1044576584710311

volume
[links to de[pression
https://brainslab.wordpress.com/essays/is-neurogenesis-in-the-hippocampus-linked-to-depression/

if we are looking for the i in me
ie the mind within the brain..

things like this wont cut it
http://wiki.answers.com/Q/What_is_a_hippocampus

but let pretend knowledge explains things
http://wiki.answers.com/Q/What_is_a_hippocampus

"Hippocampus" has three meanings
that might interest you:

1) a legendary creature with the head and forequarters of a horse and the tail of a dolphin or fish

(2) a genus of fishes consisting of the typical sea horses

[To see images, select Google's "image" button,
and type hippocampus in the search box.]

(3) a part of the brain
where information is transferred into memory.

For more information, see

http://biology.about.com/library/organs/brain/blhippocam.htm

http://www.psycheducation.org/emotion/hippocampus.htm

ok
what did the hungry hippo do?

''information is transferred into memory.''

so thats some facts
how about some opinions...!

Dear Pelly,

If you're "born again," does that mean you've got two belly-buttons?

Actual brain size is not that critical Graham, otherwise elephants
would be far smarter then humans :)

In fact there is an operation, whose name I can't remember right now,
where they remove around 40% of the brain. Its when people are
affected by seizures. Some of those people have gone on to go
through university.

Its more about how the brain is wired, which neural connections go
where and how they interact with other regions.

Dear Graham,

Fun topic. It reminds me of my less kind, younger years when the Fundamentalist Christians were referred to as Shabbies. It stood for small heads and big bottoms.

Luckily I'm far more mature, gregarious and sympathetic to the faith of others than I professed back then. :) Though I'm not sure I would get complete agreement from the flock on that point.