How Stress and Aggression Can Feed off Each Other

Article excerpt

A biological link between stress and aggression may explain why it is so hard to break cycles of violence, scientists said last night. Experiments with rats have identified a mechanism by which stress and aggression reinforce each other.

Stimulating the rat brain's aggression centre increased the production of stress hormones, which in turn led to more aggression.

The result was a 'positive feedback loop' - a cycle that led to violent rage.

Scientists believe the same mechanism probably exists in humans, and may explain why people under stress are often quick to lash out and slow to cool down.

It may be the reason why normally placid individuals can explode when pushed too far.

The system could have evolved to gear animals up to fight when cornered or facing a threatening situation, such as being caught in a trap.

Dutch and Hungarian scientists carried out five experiments using 53 rats.

First they electrically stimulated an aggression-related part of the hypothalamus, a mid-brain region associated with emotion.

The rats suddenly released the stress hormone corticosterone, which helps prepare animals for 'flight or fight'.

The scientists then removed the rats' adrenal glands to prevent natural release of corticosterone, and artificially injected the hormone. …