Five experiments were conducted on 53 male rats (rats as well as other mammals and birds and lizards have very similar neurophysiology to that of humans), electrically stimulating their brain's aggression-control centers to see if this raised blood levels of a stress hormone. The result was that raising or lowering one variable raised or lowered the other. Stress and aggression work in a positive feedback loop.
Last week I had my junior painting critique and the weeks leading up to it were extremely stressful. I found myself snapping at the most random comments and being quick to start an argument. The research done by the neuroscientists may explain why I was acting this way, or why the stress of traffic jams can lead to road rage, or why aggressive behavior triggers stress.
The study also found evidence that the activation of the aggressive system causes a stress response, not the physical exercise of fighting. The researchers electrically stimulated the rats' hypothalamic "attack center", a major brain area where attack behavior can be reliably triggered. Once stimulated, the rats suddenly released corticosterone, a stress hormone, very similar to the cortisol humans release under stress.
The results of the research show that regulating stress response may offer a new way to understand and control human violence. Medications, including as-yet undeveloped anxiety-reducers that regulate the stress response, might reduce acute stress-precipitated violence.