[Paleopsych] BH: How Stress Causes Violence, and Vice Versa
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Tue Oct 5 19:45:16 UTC 2004
How Stress Causes Violence, and Vice Versa
Identification of positive feedback loop could lead to better drug
treatments for aggression
By Gabe Romain
10/4/2004 3:25 PM
A positive feedback loop for stress and aggression has been identified
that helps explain such behaviors as road rage and may allow new drug
interventions for violent behavior.
A new study on rats has found that there seems to be a positive
feedback loop between stress hormones called glucocorticoids and
the hypothalamus--a brain area associated with a variety of
emotions including aggression.
The findings, by researchers from the Netherlands and Hungary, shed
new light on the biological underpinnings of aggression and could lead
to novel drug-based treatments for pathological violence.
"The high stress levels of glucocorticoids, rapidly produced by the
challenge-induced activation of brain mechanisms controlling
aggression, may in turn produce a fast facilitation of the very same
brain mechanisms," say the researchers. "Such mutual facilitation
could constitute a vicious circle, which would explain why aggressive
behavior escalates so easily, and why it is so difficult to stop once
it has started."
Glucocorticoids are a class of steroid hormones. The most abundant
glucocorticoid found in most organisms is corticosterone, which is
involved in regulating metabolism, immune reactions and stress
For their study, the researchers hooked up electrodes to the brains of
rats and then stimulated the region of the hypothalamus that is
involved in aggression. The stimulation caused the rats to release
corticosterone, which in turn caused the rats to display behaviors
associated with aggression, such as teeth chattering.
The results of the study indicate a fast-acting feedback loop--the
mechanism works in both directions--and suggests that stress and
aggression may be mutually reinforcing.
"It is well known that these stress hormones, in part by mobilizing
energy reserves, prepare the physiology of the body to fight or flee
during stress," says lead researcher Menno Kruk, at the
Leiden/Amsterdam Center for Drug Research. "Now it appears that the
very same hormones 'talk back' to the brain in order to facilitate
Primed for aggression
The researchers say that their findings suggest that rapid increases
in corticosterone caused by stressors unrelated to fighting may
precipitate violent behavior by lowering thresholds for attack.
Therefore, a person could be "primed" for violent behavior if they
were previously exposed to stressful situations. A bad day at work,
for example, could prime someone for violence towards other drivers
while heading home.
Further, an anticipatory increase in corticosterone in environments
previously associated with aggression could lead to place-dependent
violent tendencies in people who are nonviolent in other settings, say
Treatments for pathological violence and poor impulse control have
proven ineffective, possibly because the stress response that
accompanies stressful situations may cancel out any beneficial effects
of therapies aimed at reducing violent behavior.
Although more studies are needed, the researchers speculate that
stress-regulating drugs that help to lower acute stress-precipitated
violence could be a viable treatment option.
The research is reported in the journal Behavioral Neuroscience
(read full text).
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