According to a report published in Psychological Science, nursing mothers are just as protective of their infants as “mama bears.” Mama bears will defend cubs to the death and while mothers are not as primal in their defense, the body has adapted to the increase in stress associated with defending infants by lowering blood pressure and stress response. The same supportive adaptation was not found in mothers who bottle fed infants.

While mothers will rarely have to defend their infants from predators, like the mama bear, they may find themselves in a situation where they react with the same defensive response as mama bears. The body of the nursing mother has adapted to this stress response to keep blood pressure low and reduce the impact of fear on reaction; resulting in added courage and strength to defend their babies.

Jennifer Hahn-Holbrook, an author and postdoctoral candidate, noted that breastfeeding is recognized as the healthiest option for new babies due to the immunity and health factors associated with breastmilk nutrition, but breastfeeding seems to benefit mom just as much. The “mama bear” effect may be the body’s natural way of dealing with the stresses associated with new motherhood. She also noted that the increase in aggression was limited to defending the infant, typically with words or another form of non-violent aggressive response. “Breastfeeding mothers aren’t going to out and get into bar fights, but if someone is threatening them or their infant, our research suggests they may be more likely to defend themselves in an aggressive manner.”

Researchers used reactions from 55 women for the study. Of the 55 women, 18 were currently nursing infants, 17 were bottle feeding and 20 were not mothers. All were asked to complete computerized time-reaction tests. They were competing against a research assistant acting like a study participant that was extremely rude. The winner of the time-reaction test was allowed to press a sound button to celebrate the win. Nursing mothers celebrated with a sound blast that was louder and longer than bottle feeding mothers and participants without children.

Blood pressure was measured during the study. Breastfeeding mothers measured 12 points lower than non-mothers and 10 points lower than mothers who bottle fed their infants.

The research results mimic the results of non-human studies testing the aggression response of nursing mothers in several animal species.

Source: Julianne Holt-Lunstad, Colin Holbrook, Sarah Coyne, Ernest Lawson. University of California, Los Angeles. 5 January, 2012.