Direct Link Between Stress and Aggression

Oct. 13, 2004 -- — Scientists have found biological evidence that stress and aggression feed off of each other, contributing to a "cycle of violence" that can be tragic. When we are under stress, we are more likely to fly off the handle, and when we fly off the handle, that increases our level of stress.

It's a mutual back-scratching phenomenon, and new research shows that there is a biochemical basis for this potentially deadly spiral of stress and aggression.

Researchers in The Netherlands and Hungary found the biological connection in 53 rats, so it's not yet been demonstrated in humans, but that connection has held up in similar research in the past. They experimented with rats because it's possible to implant electrodes in the brain to turn on and off the stress sensors, and of course that sort of thing would be frowned upon if the subjects were humans.

The researchers found that when they turned on the electrodes to convince the rats that they were in a stressful situation, the level of corticosterone soared upward in their bloodstreams. That's the major hormone produced by bodies -- both rats and humans -- to help us get through stressful situations.

What happened next was very revealing. The rats became very aggressive, even attacking other rats that had been drugged to the point that they were almost lifeless. That, in turn, stimulated the attacking rats to produce more of the hormone, thus plunging them into a hopeless cycle of stress and violence.

The researchers found they could turn the cycle on and off just by regulating the hormone, and the rats could care less that their opponents were under "profound sedation," according to a report on their study in the October issue of "Behavioral Neuroscience," which is published by the American Psychological Association.

It gets worse. The stressed rats didn't even need another rat to get riled up.

"The confrontation with an opponent apparently is not required," they report.