Don’t Mess With Breast Feeding Mothers

Many mammals tend to be extremely aggressive when it comes to protecting their young, and one explanation is the biological effect of lactation on stress reduction. It turns out that humans are no different:

Here we report the first behavioral evidence for heightened aggression in lactating humans. Breast-feeding mothers inflicted louder and longer punitive sound bursts on unduly aggressive confederates than did formula-feeding mothers or women who had never been pregnant. Maternal aggression in other mammals is thought to be facilitated by the buffering effect of lactation on stress responses. Consistent with the animal literature, our results showed that while lactating women were aggressing, they exhibited lower systolic blood pressure than did formula-feeding or never-pregnant women while they were aggressing.

What’s interesting is that the notion of less stress leading to increased aggressiveness runs counter to the societal stereotype of high strung people flipping out over minor things. It turns out that in breast feeding mothers a decrease in stress lessens concerns about the consequences of increased aggressiveness, and that allows mothers to be extra vigilant in protection their young. Although the process seems counter-intuitive, it makes sense when you think about less stress leading to more “social aggression” (e.g. talking to the opposite sex in a bar).

If there are any professional MMA fighters out there, the study is a point in favor of the “sit and meditate” pre-fight routine rather than that the “think about all the bad things your opponent said about you” routine.
Hahn-Holbrook J., Holt-Lunstad J., Holbrook C., Coyne S.M., & Lawson E.T. (2011). Maternal defense: breast feeding increases aggression by reducing stress. Psychological science, 22 (10), 1288-95 PMID: 21873570

One Response to Don’t Mess With Breast Feeding Mothers

  1. Tasha says:

    Wow, this is really interesting. It seems ironic, but it actually makes sense. Less stress causing aggressive behavior, who would’ve thought!

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