Stress Shrinks Hippocampus of the Brain
There is evidence and suggestion that excessive chronic stress such as PTSD (post traumatic stress disorder) may shrinks the hippocampus of the brain. The hippocampus of the brain is major component of the brain partially responsible for learning, memory, and spatial navigation. The hippocampus is also the first area of the brain that experiences damage and shrinkage in Alzheimer's Disease. Brain shrinkage is also known as atrophy.
It is true that everyone's brain shrink with advancing age. However, the hippocampus shrinkage that we are talking about here is shrinkage that is in excess of normal aging.
While there are some debate as to whether it is stress that caused the decrease in hippocampus volume or whether small hippocampus volume in the first place makes a person more susceptible to stress, below are some evidence that suggests the former.
What Shrinks the Hippocampus?
Three mood disorder conditions that can shrink the hippocampus are depression, PTSD (post-traumatic stress disorder), and bipolar disorder.
We know there is a link between depression and stress. Both prolonged depression and stress can cause structural and functional changes in the brain. And the amount of changes correlates to the number of years depressed or stressed. See video from Rockerfeller University on right.
Proteins called kainate receptors have been implicated in depression. And animal studies has found that rats under stress generated more of these KA1 kainate receptors proteins. A Rockerfeller University article says ...
"Stress and depression are known to cause a reversible retraction of dendrites in certain brain cells, particularly in the hippocampus"
According to The Chemistry of Calm, prolonged excessive cortisol stress hormone can lead to brain degeneration such as memory problems as well as insulin resistance and fat storage. Obesity, diabetes, and insulin resistance is associated with increased risk of Alzheimer's.
Hippocampus - Memory and Learning Center of the brain
Exercise can Reverse Hippocampus Shrinkage
Retraction of dendrites is definitely not a good thing. However, the key word is "reversible". The hippocampus shrinkage can stop when depression is addressed and when stress is removed -- "brains replace their retracted neurons once the stress is removed" is how the article phrased it.
In addition, it you add in physical exercise, the hippocampus volume can experience brain growth. So it is possible that the hippocampus shrinkage can be reversed as stated in psycheducation.org. Although to what extent is difficult to determine.
According to scientificamerican.com, some possible factors implicated in the stress-related hippocampus shrinkage are due to increase in stress-hormone cortisol, increased glutamate levels, and decreased brain-derived neurotropic factor (BDNF).
Exercise have been known to increase brain-derived neurotropic factors and is one of the best things you can do to maintain brain health. So it makes sense that exercise can halt the shrinkage.
Chronic Stress Damaging to Brain
There have been ample evidence that stress hormone cortisol can kill brain cells (especially those in the hippocampus).
Study found that chronic stress impairs working memory and pre-frontal cortex functioning. Study by Dr. Yan and juvenile rats found that rats with repeated stress had significant loss of glutamate receptors resulting in poorer pre-frontal cortex functioning which is responsible for executive decision making and working memory. [reference]
-  PsychEducation: Can the Shrinkage Be Reversed?
-  The Rockefeller University » Protein found linking stress and depression
-  News Blog: Stressing the Hippocampus: Why It Matters
A vital part of your brain is named after the animal that its odd, twisting shape resembles: the seahorse, genus Hippocampus.
Article was written October 2011 and is only opinion at the time of writing. Author is not a medical professional.