Breast-feeding has well-documented benefits. Studies have shown it nourishes babies while fighting off infections and even boosting IQ. Now a study in Pediatrics suggests nursing also may protect infants from neglect.

In a study of 6,621 Australian children over 15 years, researchers found that those who were breast-fed were far less likely to be neglected or abused by their mothers. Babies who weren't breast-fed were more than 2½ times as likely to be maltreated by their mothers as those who were nursed for four months or more, the study shows. There was no link between breast-feeding and the risk of maltreatment by fathers or others.

Women who don't breast-feed can still be wonderful mothers, of course, and both parents can feel physically and emotionally close during bottle feeding, says author Lane Strathearn of Houston's Baylor College of Medicine.

But a hormone released during nursing, called oxytocin, may amplify that bond, Strathearn says.

Studies show that oxytocin has a powerful effect on the brain: It makes people feel less anxious and stressed but more calm, trusting and connected, Strathearn says. In animals, both nursing and oxytocin stimulate parts of the brain that are involved in maternal behavior.

Of course, many factors contribute to child neglect, Strathearn says.

To find out whether breast-feeding should get the credit for reducing the risk, Strathearn considered details such as the mother's age, race, marital status, education, employment and use of tobacco and alcohol. He also looked at whether mothers were anxious or depressed, their attitudes toward pregnancy and their babies and how much they played with or talked to their children.

Of all of these factors, breast-feeding remained the strongest predictor of neglect, Strathearn says.

Still, the paper cannot prove that breast-feeding made women better mothers, says Brett Collett, an attending psychologist at Seattle Children's Hospital. That's because researchers didn't randomly assign women to breast-feed or bottle-feed — an experiment that would be unethical, given breast milk's medical advantages.

Collett says the researchers may have it backward. Instead of breast-feeding turning women into good mothers, it's possible that good mothers are more likely to breast-feed. He notes that it can take perseverance to breast-feed, which can be difficult, exhausting and even painful at first.

"Some women may not be able to breast-feed, and that may not have anything to do with maltreatment," Collett says, noting that obstacles to nursing include medical problems as well as demanding jobs that don't give women the opportunity to breast-feed or pump milk.

"We don't want to induce guilt on the part of moms who aren't able to persevere" with nursing, Collett says. "There are a lot of different pathways to healthy attachments" between mothers and babies.

And Strathearn says it's possible that both explanations of his findings are valid: Although nurturing mothers may be more likely to nurse, the act of breast-feeding further strengthens that commitment to child rearing.

With 900,000 American children maltreated each year, Strathearn says, the subject deserves more study.