Here is a quote from an article I was just reading:

"In experimental animals, chronic stress has been shown to cause dendritic atrophy or even cell death and to inhibit neurogenesis in the hippocampus3 and prefrontal cortex.4     We know that stress hurts the brain, but causing dendritic atrophy means that the branches between neurons fade away!  We want to increase connectivity of nerve cells (create neuroplasticity), not decrease them!

Subtle Neurologic Compromise as a Vulnerability Factor for Combat-Related Posttraumatic Stress DisorderResults of a Twin Study FREE

Tamara V. Gurvits, MD, PhD; Linda J. Metzger, PhD; Natasha B. Lasko, PhD; Paul A. Cannistraro, MD; Alexandra S. Tarhan, MD, PhD; Mark W. Gilbertson, PhD; Scott P. Orr, PhD; Anna M. Charbonneau, BA; Michelle M. Wedig, BS; Roger K. Pitman, MD
Arch Gen Psychiatry. 2006;63(5):571-576. doi:10.1001/archpsyc.63.5.571.