Stress Harms the Brain & Nerves
Part of the fight-or-flight reaction affects short-term memory recall. Stress hormones suppress activity in the prefrontal cortex, which also processes concentration, inhibition and rational thought. The social and intellectual brain tasks that might come to you automatically under normal conditions are also temporarily shelved when you are facing acute stress. Your powers of observation and focus are heightened, but calling up short-term memories is not high on the list of operations necessary for survival.
Another part of your brain that handles memories, the hippocampus, is more active when you are under stress. When you are experiencing an intense, emotional episode, neurotransmitters signal the hippocampus to store it away in long-term memory. Back in prehistoric times, this memory task would have been essential to avoiding stress-provoking environmental factors in the future. (“Note to self: Remember to run from the tiger!)
What Happens After Serious Trauma?
The hippocampus contains many receptors for stress hormones, and is proven to be very vulnerable to stress. In addition to its role as the center for learning, the hippocampus processes stressful memories. It suffers alarming physical damage among survivors of extreme, life-threatening trauma. In two separate studies—one examining combat veterans, the other survivors of sexual abuse—victims' brains were scanned. The hippocampi of those who had experienced severe trauma were up to 25% smaller than average.