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October 25, 2007

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Hormone found to predict mother-child bonding

Oct. 15, 2007
Courtesy Association for 
Psychological Science
and World Science staff

Lev­els of a hor­mone cir­cu­lat­ing in a preg­nant wom­an pre­dict how close­ly she’ll bond with her ba­by, re­search­ers have found.

Hu­mans are hard-wired to form en­dur­ing bonds with oth­ers; key among these is the mother-in­fant bond. Ev­o­lu­tion­ari­ly speak­ing, it’s in a moth­er’s in­ter­est to fos­ter her child’s well-being—but some moth­ers seem a bit more ma­ter­nal than oth­ers do. 

A mother and child in Senegal. (Courtesy Richard Nyberg, USAID/Senegal)
In an­i­mals, ox­y­to­cin, dubbed the hor­mone of love and bond­ing, is elicited dur­ing sex­u­al in­ter­course; is in­volved in main­tain­ing close rel­a­t­ion­ships; and is crit­i­cal for par­ent­ing. An­i­mals with low ox­y­to­cin lev­els are slower to re­trieve wan­der­ing pups, for in­stance. 

But the hor­mone’s role in hu­man bond­ing has been stud­ied lit­tle, ac­cord­ing to Ruth Feld­man, a psy­ch­olo­gist at Bar-Ilan Un­i­vers­ity in Ra­mat-Gan, Is­ra­el. 

Feld­man and col­leagues meas­ured lev­els of ox­y­to­cin in the blood­stream of 62 wom­en dur­ing their first and third trimesters of preg­nan­cy, and in their first month af­ter giv­ing birth. 

They al­so watched the moth­ers and chil­dren in­ter­act, rat­ing at­tach­ment lev­els in four cat­e­gories: gaze, tou­ch, af­fect (ex­pres­sion) and vo­cal­iz­a­tion. The moth­ers also com­plet­ed a sur­vey and in­ter­view on their bond-re­lat­ed thoughts, feel­ings, and be­hav­iors. The re­search­ers then com­put­ed the link be­tween ox­y­to­cin lev­els and bond­ing.

Moth­ers with high ox­y­to­cin ear­ly in preg­nan­cy en­gaged in more bond­ing af­ter birth, the re­search­ers found. Moms with high­er lev­els of ox­y­to­cin across the whole time pe­ri­od, they added, re­ported more be­hav­iors that help form ex­clu­sive rel­a­t­ion­ships, such as sing­ing a spe­cial song to the baby, or bath­ing and feed­ing them in a spe­cial way. These moth­ers were al­so more pre­oc­cu­pied by thoughts of check­ing on the in­fant, its safe­ty when they weren’t around, and its fu­ture. 

The work, pub­lished in the No­vem­ber is­sue of the re­search jour­nal Psy­cho­log­i­cal Sci­ence, shows ox­y­to­cin is re­lat­ed to both the men­tal and the be­hav­ior­al as­pects of bond­ing—and that it func­tions si­m­i­lar­ly across spe­cies, Feld­man said.

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Levels of a hormone circulating in a pregnant woman predict how close ly she’ll bond with her baby, researchers have found. Humans are hard-wired to form enduring bonds with others; key among these is the mother-infant bond. Evolution ari ly speaking, it’s in a mother’s interest to foster her child’s well-being—but some mothers seem a bit more maternal than others do. In animals, oxytocin, dubbed the hormone of love and bonding, is elicited during sexual intercourse; is involved in maintaining close rel ationships; and is critical for parenting. Animals with low oxytocin levels are slower to retrieve wandering pups, for instance. But the hormone’s role in human bonding has been studied little, according to Ruth Feldman, a psychogist at Bar-Ilan Un ivers ity in Ramat-Gan, Israel. Feldman and colleagues measured levels of oxytocin in the bloodstream of 62 pregnant women during their first and third trimesters of pregnancy, and the first month after birth. They also watched the mothers and children interact, rating attachment levels in four categories: gaze, affect, touch, and vocal ization. After the mothers completed an extensive survey and an interview on their bond-related thoughts, feelings, and behaviors, the researchers computed the link between oxytocin levels and bonding. Mothers with high oxytocin ear ly in pregnancy engaged in more of bonding behaviors after birth, the researchers found. Moms with higher levels of oxytocin across the whole time period, they added, reported more behaviors that support form ation of exclusive rel ationships, such as singing a special song to the infant, or bathing and feeding them in a special way. These mothers were also more preoccupied by thoughts of checking on the infant, the infant’s safety when they are not around, and the infant’s future. This study, published in the November issue of the research journal Psychological Science, show oxytocin is related to both the mental and the behavioral aspects of bonding—and that it functions similar ly across species, Feldman said.