Exercise is considered to have protective qualities against the onset of depression. Regular exercise may help prevent the onset of depression, reduce its worst effects should it occur, and help to speed recovery. Similarly, regular exercise is known to help with stress reduction and building resilience against stress, but only recently have we discovered the biological mechanisms involved.
The hippocampus is an area of the brain that has multiple functions. It is also the area of the brain that seems most vulnerable to stress. People suffering with post-traumatic stress syndrome (PTSD), for example, experience an extreme form of stress and this can result in atrophy (wasting away) of the hippocampus. This can also be seen as a result of long-standing depression.
What is interesting about regular exercise is that it generates new neurons in the ventral region of the hippocampus. This has previously represented something of a puzzle, as the generation of new neurons should, in theory, lead to more anxiety. In fact the opposite effect is effect is seen and finally researchers believe they understand what is happening.
Gamma-aminobutyric acid (GABA) is a neurotransmitter that acts pretty much like a brake for neural activity. GABA reduces anxiety and the more we have of it the greater is our ability to suppress those excitable neurons and the calmer we feel. Recent experiments reported in the Journal of Neuroscience shows that regular exercise has the effect of leading to a spike in activity in GABA when stressful situations are encountered.
The reported experiment used two groups of mice. One group had access to a running wheel and the other did not. Mice are naturally very active creatures and if given the opportunity will run over two miles every night. After six weeks had passed both groups of mice were exposed to a cold-water shock for a short time. In mice that had exercised, more GABA was produced in the brain and they reacted far more slowly to the stressful situation.
Exercise may also have an edge over relaxation. Researchers from the University of Maryland School of Public Health found that exercise and quiet rest seem to be equally effective when it came to reducing anxiety levels. Using a set of photographs developed by the National Institute of Mental Health Center for Emotion and Attention, designed to elicit a range of emotions, researchers found that the anxiety levels of people who rested climbed back up around 20 minutes later. By contrast, those who exercised maintained reduced anxiety levels. This level of persistence adds yet another layer of interest as to the neurological benefits that accompany exercise.
T. J. Schoenfeld, P. Rada, P. R. Pieruzzini, B. Hsueh, E. Gould. Physical Exercise Prevents Stress-Induced Activation of Granule Neurons and Enhances Local Inhibitory Mechanisms in the Dentate Gyrus. Journal of Neuroscience, 2013; 33 (18): 7770 DOI: 10.1523/JNEUROSCI.5352-12.2013
University of Maryland (2012, September 13). Exercise may protect against future emotional stress, study shows. ScienceDaily. Retrieved July 10, 2013, from http://www.sciencedaily.com