The researchers say early maturation only predicted physical aggression when combined with low maternal nurturance.

The study of 330 fifth-grade girls, led by Sylvie Mrug and published in the Archives of Pediatrics & Adolescent Medicine, found one-fourth of the girls had matured early -- that is, they began their period one year before the average age for females of their racial and ethnic group. These girls were more likely to be delinquent, but not aggressive, unless they'd had low levels of parental nurturance.

"As adults, early-maturing girls demonstrate lower academic and occupational achievement and report lower relationship quality and life satisfaction," the study authors said in a statement. "It is thus important to identify protective factors that may mitigate negative effects of early maturation on girls' adjustment."