Early puberty 'makes girls more aggressive'

The study was carried out at the University of Queensland.

Girls who go through puberty before their 12th birthdays are more aggressive and more likely to steal, fight and take drugs than their later-blooming friends.

A University of Queensland study has found that girls who experience puberty early are "significantly" more aggressive than their later developing peers by age 14.

It has also found there's no marked difference between boys' and girls' aggression levels when at the same stage of puberty.

The findings stem from Australia's largest longitudinal study, which tracked more than 8000 mothers and their children over 21 years.

Lead author and sociologist Professor Jake Najman says girls who are early bloomers are more likely to steal, fight, smoke and take drugs, but the reasons why are not conclusive.

It's also not known whether these characteristics carry on to womanhood.

Prof Najman says the findings, coupled with children reaching puberty earlier and earlier, may explain why girls are increasingly involved in anti-social behaviour such as drinking, smoking, drug-taking and bullying.

"It links together, in a sense, that what we're seeing is probably more aggression and delinquent behaviour by females at younger ages as a social trend," he said.

"... we're seeing women behaving more like men in terms of their behaviours."

The study also disproves the belief that boys are more aggressive than girls because of higher testosterone levels.

Prof Najman said the study showed that intervention programmes aimed at addressing anti-social behaviour should be introduced before puberty to have the most effect.

The study has been published in the Australian and New Zealand Journal of Criminology.

- AAP