Here's a link to one review by DocJohn:

http://psychcentral.com/news/2009/02...gene/4283.html

In general, stress will cause reversible strain on any system, if the stress is not too great; if it is more than that particular system can handle, more-or-less permanent strain will develop. That is how stress results in "mental illness". If you stretch a rubber band, and then let go, it will snap back to its original position -- unless you have stretched it too far, and it breaks. Then you have a big job getting it back together.

As far as brain cells are concerned, I imagine that cell pathways or connections will develop that reinforce bad coping mechanisms if the strain is too great, or maybe some brain cells will atrophy and die. Good coping will strengthen healthy signal pathways amongst brain cells (neurons).