FRIDAY, Sept. 28, 2007 (HealthDay News) -- Children with older brothers are more likely to become increasingly aggressive over time than children with older sisters, U.S. research suggests.
A team at the University of California, Davis, observed 451 sibling pairs, ages 9 through 18, along with their parents.
The researchers gathered information about the aggressive behavior of the children and had the parents describe economic pressures on the family, such as paying bills. There was also an assessment of the hostility parents directed toward their children during family interactions.
Besides the older-brother finding, the researchers also concluded that older siblings with younger sisters become less aggressive, while older siblings with younger brothers have fairly stable levels of aggression over time. Older siblings of either gender who are aggressive tend to have younger siblings who are also aggressive, and vice-versa, the team found.
The researchers also concluded that parents' hostility also played a role in the development of aggression in their children. Family economic pressure predicted increased aggression in children indirectly, through its association with parental hostility, the study said.
"Understanding the factors associated with the development of aggression is essential to the design and implementation of effective intervention efforts aimed at decreasing aggression and its negative consequences," lead author Shannon Tierney Williams said in a prepared statement. "These finding suggest that such an intervention may benefit from including both siblings and parents in these efforts."
The findings are published in the Sept./Oct. issue of the journal Child Development.
The American Academy of Pediatrics has more about aggressive behavior in children.