Girls who go through puberty at a younger age have increased levels of aggression, says a study from the University of Queensland. Study lead author, sociologist Professor Jake Najman, suggests girls who hit puberty before the age of 12 may have disrupted social networks, increased parental conflict and different desires and expectations to their peers. The report in the Australian and New Zealand Journal of Criminology also found self-reported aggression/delinquency by females is comparable to the rates in young males. Professor Najman says there is evidence of a narrowing gap between male and female health risk behaviours. “Females are as willing as males to engage in types of aggressive or delinquent behaviours," he said in a press release, adding that "This shows that there may simply be a greater acceptance of these behaviours in females than has previously been the case.” The data were derived from the Mater University Study of Pregnancy and its outcomes, Australia's largest longitudinal study of over 8000 mothers and their children over 21 years. The study findings are backed up by the Australian Institute of Health and Welfare who showed young females now smoke at rates equal to or higher than males, binge drink alcohol at similar rates and are closing the gap with some illicit drug use.