What causes crybabies?

New research in primates suggests that it's not just overanxious parenting.


Carol Lloyd
April 3, 2008 7:40PM (UTC)

Next time you hear the theory that it's the mother's fault her baby screams every time she attempts to leave the room, try casually saying, "Sounds like you guys haven't read that 'variation at the mu-opioid receptor gene (OPRM1) influences attachment behavior in infant primates' from the latest issue of Proceedings of the National Academy of Sciences" and see if you don't get the floor.

This study of monkey genes, reported by New Scientist, suggests that intense infant and toddler attachment may not be a matter of clingy helicopter mommies creating their own crawling, bawling excuses for Valium addiction. If rhesus macaques offer a window into human experience, the crybaby phenomenon may have biological roots.

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Neuroscientist Christina Barr of the National Institute on Alcohol Abuse and Alcoholism in Bethesda, Md., told the New Scientist that the bodies of infant monkeys are like human infants in that they release pleasure-inducing substances called opioids when they spend time with their mothers -- chemicals that act via the same brain receptors as morphine. But some monkeys (again, like humans) have a gene mutation that seems to intensify this pleasure and make withdrawal from it more painful. For those 25-30 percent of the monkeys with the genetic variation, maternal separation produces unremitting distress with repeated separations; those monkeys seem resistant to weaning and developing peer relationships. In contrast, monkeys without this extra attachment gene exhibit decreasing levels of distress with repeated maternal separation and spend more time exploring the world.

While this study may be good news for mothers and fathers who blame their own parenting style for their children's insatiable neediness, it delivers its dose of bad news as well. The genetic variation that creates intense maternal attachment is also associated with an increased vulnerability to alcohol and drugs. Another study found that macaques with the genetic mutation drink more alcohol than normal monkeys when given the chance, leading Barr to compare a genetic proclivity to maternal attachment with a sort of proto-addiction. "In a sense it's very similar to effects that you would see during periods of intoxication and withdrawal," Barr told Science Central.

This may not completely staunch the theories that anxious attachment derives from negligent or obsessive parenting (another chapter of the endless tome "It's all Mom's fault!"). But it does offer one alternative explanation for how parents can raise one child who easily adjusts to the inevitable separations from caregivers and another who just won't let go.


Carol Lloyd

Carol Lloyd is currently at work on a book about the gentrification wars in San Francisco's Mission District.

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