LONDON (Reuters) -
Serotonin, the brain chemical linked to
mood, plays a key role in regulating emotions such as
aggression, British researchers said on Thursday.

Serotonin, the nerve-signaling chemical targeted by many
antidepressants, appears to keep aggressive social responses in
check, Molly Crockett, a psychologist at the University of
Cambridge and colleagues reported in the journal Science.

The chemical's precise role in impulse control has been
controversial but this study is one of the first to actually
show a causal link, Crockett said.

“Because we directly manipulated serotonin levels and
observed an effect on behavior we can say there is a causal
link between serotonin and aggressive responses,” Crockett said
in a telephone interview.

Their research also helps explain why some people become
combative or aggressive when hungry because the essential amino
acid needed for the body to create serotonin is only obtained
through diet.

The team used this knowledge to manipulate serotonin levels
in 20 healthy volunteers who were then asked to play a
situation game that tested their responses to fair and unfair
offers of money.

People with lower serotonin levels were far more likely to
deprive other players of money, even though they lost out as
well, as a way to punish the person who made the offer, the
researchers said.

“It is an anger-driven response,” Crockett said.

This knowledge could help doctors treat people with
depression and anxiety disorders by teaching them ways to
regulate emotions during decision making, especially in social
situations, she added.