blow-ups such as road
rage may have a biological basis, according to a new study.
Blood tests of people who
display the hostile outbursts that characterise a psychiatric
illness known as intermittent explosive disorder show signs of inflammation,
"What we show is that
inflammation markers [proteins] are up in these aggressive individuals,"
said Dr Emil Coccaro, professor and chair of psychiatry and behavioural
neuroscience at the University of Chicago.
Currently, medication and behaviour
therapy are used to treat intermittent explosive disorder, which affects about
16 million Americans, according to the US National Institute of Mental Health.
But these methods are effective in fewer than 50% of cases, the study authors
Essential to seek
Coccaro now wants to see if
anti-inflammatory medicines can reduce both unwarranted aggression and
inflammation in people with this disorder.
Meanwhile, he said, it's
important for those with the condition to seek treatment, rather than expect
loved ones and others to live with the episodes of unwarranted hostility.
Experts began looking at
inflammation and its link to aggressive behaviour about a decade ago, Coccaro
said. The new research, published online in JAMA Psychiatry, is believed
to be the first to show that two indicators of inflammation are higher in those
diagnosed with the condition than in people with other psychiatric disorders or
good mental health, he said.
The body-wide inflammation
also puts these people at risk for other medical problems, including heart
attack, stroke and arthritis, Coccaro noted.
Still, it's not known if
inflammation triggers aggression or if repeated acts of aggression lead to
inflammation, Coccaro said. Although the two are linked, the study does not
establish a cause-and-effect relationship.
Initial controversy about
whether intermittent explosive disorder is a "real" illness has
subsided as more research has been done, Coccaro added.
Those diagnosed with the
condition have episodes of impulsivity and aggression that are way out of
proportion to the stressor. They lose control, breaking property or trying to
hurt people. For example, they might blow up at a store clerk for moving too
slowly or making a minor mistake.
For the study, Coccaro
looked at levels of two types of indicators of inflammation in blood:
C-reactive protein and interleukin-6. Elevated levels of these proteins have
been linked with aggressive and impulsive behaviours in people and animals.
Nearly 200 people
participated in the study. 69 had intermittent explosive disorder, 61 had
psychiatric disorders not involving aggression and 67 were in good mental
"The levels of chronic
inflammation are about twice as great in [intermittent explosive disorder]
compared with healthy subjects," Coccaro found.
Behaviour influenced by biology
The blood test to evaluate
inflammation won't be a diagnostic test, however, because the disorder is
diagnosed by observation and reports of behaviour.
Mark Dombeck, a
psychologist in Oakland, California, said the new study is interesting even though
it has no immediate clinical application. "It's not possible to say
whether the inflammation is contributing to the aggression or whether the
aggression is contributing to the inflammation," he agreed.
But even if inflammation is
eventually found to be a cause of intermittent explosive disorder, Dombeck said
it still may not lead to a simple solution. "Behaviour is certainly
influenced by biology, but it's influenced by a lot more than that," he
Eliminating the cause of a
disorder, he noted, is not always enough to change the behaviour once it is
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