London, Feb 26 : Mood swings, aggressiveness and angst in teenagers can be attributed to the significantly different brain structures of some teens, according to a study.
Australian scientists have demonstrated that teens who repeatedly have fights with their parents possess a different brain structure than their more relaxed peers.
One brain area, the amygdala, was found to be enlarged in teenagers prone to having prolonged and aggressive arguments.
A lack of balance in the size of two other regions in the brain cortex was linked to aggression and "dysphoria" - anxious and "whining" behaviour - but only in boys.
For the study, scientists from the University of Melbourne filmed one-on-one issue discussions or "problem-solving interactions" (PSIs) between 137 adolescents aged 11 to 14 and their parents.
The topics of the discussions were deliberately chosen to be provocative. Examples included (adolescent) "lying" and "talking back to parents".
Scores were allocated to the behaviour shown by each youngster according to a standard scale used by psychologists which included traits such as anger, contempt, belligerence, anxiety, or being "happy" or "caring".
Fllowing this, the brain structure of each adolescent was mapped by a magnetic resonance imaging (MRI) scanner, which focused on the "limbic system," the part of the brain that deals with emotion.
In particular, the scientists measured the size of the amygdala, anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC), as well as the relative size of the brain regions.
The scientists found that adolescents with larger amygdalas were more likely to have long and moody interactions with their mothers.
Amygdala is well known as a centre of emotional reactivity, and an enlarged amygdala has been linked to substance abuse and depression in young people. The two other regions, the anterior cingulate and orbitofrontal cortices, both at the front of the brain, are involved in regulating behaviour.
"Teenagers have a mismatch going on. They have a rapidly-developing amygdala but much slower development of the structures that regulate behaviour. Parents often feel reassured when they hear that," Nature quoted lead author Nicholas Allen, as saying.
The team also revealed that young men with more symmetrical right and left brain hemispheres are more likely to argue back to their parents than those with a relatively larger left half of their brains.
"This paper fills in a missing link between structural brain differences in these key regions of adolescents' brains and behaviour in a natural situation involving conflict," said. Michael Posner, a psychologist at the University of Oregon in Eugene.
The study is published in the journal Proceedings of the National Academy of Sciences.