When levels of a brain chemical called serotonin are low, which often occur when someone hasn't eaten or is stressed, it may be more difficult for individuals to control their anger and, in turn, make them more prone to aggression, UKL researchers say.
For the study, healthy volunteers' serotonin levels were altered by manipulating their diet.
The researchers then scanned the volunteers' brains using functional magnetic resonance imaging (fMRI) as they viewed faces with angry, sad, and neutral expressions.
The research revealed that low brain serotonin made communications between specific brain regions of the emotional limbic system of the brain (a structure called the amygdala) and the frontal lobes weaker compared to those present under normal levels of serotonin.
The findings suggest that when serotonin levels are low, it may be more difficult for the prefrontal cortex to control emotional responses to anger that are generated within the amygdala.
Using a personality questionnaire, they also determined which individuals have a natural tendency to behave aggressively.
In these individuals, the communications between the amygdala and the prefrontal cortex was even weaker following serotonin depletion.
As a result, those individuals who might be predisposed to aggression were the most sensitive to changes in serotonin depletion.
The study was recently published in the journal Biological Psychiatry.