WEDNESDAY, Sept. 7 (HealthDay News) -- Breast-feeding mothers protect their babies and themselves more aggressively than mothers who bottle-feed or women without children, researchers say.

The study of 18 nursing mothers, 17 formula-feeding mothers and 20 non-mothers also found that aggression in breast-feeding moms is associated with reduced blood pressure.

This suggests that breast-feeding helps lower the body's typical stress response to fear, which gives women extra courage in defending their babies and themselves, according to the authors of the study in the September issue of the journal Psychological Science.

"Breast-feeding has many benefits for a baby's health and immunity, but it seems to also have a little-known benefit for the mother," lead author Jennifer Hahn-Holbrook, a postdoctoral fellow in the psychology department at the University of California, Los Angeles, said in a journal news release.

"It may be providing mothers with a buffer against the many stressors new moms face while at the same time giving mothers an extra burst of courage if they need to defend themselves or their child," she added.

The aggression isn't uncontrolled.

"Breast-feeding mothers aren't going to go 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," Hahn-Holbrook said.

More information

The U.S. National Institute of Child Health and Human Development has more about breast-feeding.