Serotonin affects regions in the brain that regulate anger. New research now shows that levels of serotonin can fluctuate under stress and also when a person is hungry. When serotonin levels are low, it is more difficult to control emotional responses to anger.
This finding will likely be used in new treatments and strategies for helping people with aggression issues. Hopefully the data can be used to address those individuals with psychiatric disorders that manifest in violent outbursts.
It has been known that serotonin had a relationship to aggressive behavior. This is the first study though to show how this chemical helps regulate behavior in the brain as well as why some individuals might be prone to more violent responses.
Healthy volunteers agreed to suppressed serotonin levels. Their diet was altered and on the serotonin depletion day, they were given amino acids that lacked tryptophan, a necessary component for the creation of serotonin. On scheduled placebo days, they were given normal amounts of tryptophan.
The volunteers brains were scanned using fMRI technology while they looked a photos of people’s faces expressing various types of emotion. Researchers watched the way the various regions of the brain communicated the visual information.
They found that a structure called the amygdala, the emotional limbic system of the brain, communicated poorly with the frontal lobes when serotonin levels were low. Through interviews and questionnaires they determined that the people with low serotonin were more likely to use aggressive behavior with serotonin depletion.
For people with intermitten explosive disorder (IED), for instance, these findings could be very valuable. This disorder causes and uncontrollable violent outburst which is often triggered by an angry facial expression or other cue.
We are hopeful that our research will lead to improved diagnostics as well as better treatments for this and other conditions,” said Luca Passamonti when discussing the research that she and her colleagues at the Cognition and Brain Sciences Unit of the Medical Research Council in Cambridge.