The hormone best known for its role in inducing labor may influence our abilityto bond with others, according to researchers at the University of California,San Francisco.
In a preliminary study, the hormone oxytocin was shown to be associated withthe ability to maintain healthy interpersonal relationships and healthypsychological boundaries with other people. The study appears in the Julyissue of Psychiatry.
"This is one of the first looks into the biological basis for human attachmentand bonding," said Rebecca Turner, PhD, UCSF adjunct assistant professor ofpsychiatry and lead author of the study. "Our study indicates that oxytocinmay be mediating emotional experiences in close relationships.""The study builds upon previous knowledge of the important role oxytocin playsin the reproductive life of mammals. The hormone facilitates nest building andpup retrieval in rats, acceptance of offspring in sheep, and the formation ofadult pair-bonds in prairie voles. In humans, oxytocin stimulates milkejection during lactation, uterine contraction during birth, and is releasedduring sexual orgasm in both men and women.
Turner and her colleagues tested the idea that oxytocin is released in responseto intense emotional states in addition to physical cues. Twenty-sixnon-lactating women between the ages of 23 and 35 were asked to recall andre-experience a past relationship event that caused them to feel a positiveemotion, such as love or infatuation, and a negative emotion, such as loss orabandonment. Because massage done on rats had previously been shown toinfluence oxytocin levels, the participants also received a 15-minute Swedishmassage of the neck and shoulders. Blood samples were taken before, during,and after each of the three events to measure baseline oxytocin levels in thebloodstream and any change.
The results, on average, were of borderline significance - relaxation massagecaused oxytocin levels to rise slightly and recollection of a negative emotioncaused oxytocin levels to fall slightly. Recollection of a positive emotion,on average, had no effect.
What surprised the researchers, however, was how differently each womanresponded. Some participants showed substantial increases and decreases whileothers were largely unaffected.
"We decided to look at the interpersonal characteristics of individual women tosee if there was a correlation with changes in their oxytocin levels," saidTurner, who is also the director of Student Research at the California Schoolof Professional Psychology, Alameda campus. "We found a significant differencebetween women who reported distress and anxiety in their relationships andwomen who were more secure in their relationships."
Different questionnaires, including the Inventory of Interpersonal Problems andthe Adult Attachment Scale, were used to assess each woman's previousexperiences with personal and close relationships. The results weresignificantly correlated with the recorded changes in bloodstream oxytocinlevels.
Women whose oxytocin levels rose in response to massage and remembering apositive relationship reported having little difficulty setting appropriateboundaries, being alone, and trying too hard to please others. Women whoseoxytocin levels fell in response to remembering a negative emotionalrelationship reported greater problems with experiencing anxiety in closerelationships.
"It seems that having this hormone "available" during positive experiences, andnot being depleted of it during negative experiences, is associated withwell-being in relationships," said Turner.
In addition, women who were currently involved in a committed relationshipexperienced greater oxytocin increases in response to positive emotions thansingle women. The researchers speculate that a close, regular relationship mayinfluence the responsiveness of the hormone, said Turner.
These preliminary findings bring up some intriguing questions, said TeresaMcGuinness, MD, PhD, UCSF clinical psychiatry faculty member and co-author ofthe paper. Because oxytocin is released in men and women during sexual orgasm,it may be involved in adult bonding, said Turner. There is also speculationthat in addition to facilitating lactation and the birthing process, thehormone facilitates the emotional bond between mother and child.
"Evolutionarily speaking, it makes sense that during pregnancy and thepostpartum, both a woman's body and her mind would be stimulated to nurture herchild," said Turner.
Oxytocin may also play a role in the higher levels of depression andinterpersonal stress seen in women, said Turner. According to mostpsychiatrists, women experience depression twice as often as men and tend to bemore affected by relationship difficulties. Turner and her colleagues hopethat their work on oxytocin will guide future research on the psychiatricconditions of men and women.
"Our results provide the groundwork for further studies looking at the wayhormones may be affecting human attachment," said Turner. "We know thatoxytocin is one of the hormones that can facilitate bonding in other animals,but this is the first step in exploring whether it plays a role in theemotional behavior of humans."
In addition to Turner and McGuinness, authors of the paper include MargaretAltemus, MD, assistant professor of psychiatry at Cornell University MedicalCollege; Teresa Enos, PhD, a graduate of the California School of ProfessionalPsychology; and Bruce Cooper, PhD, professor at the California School ofProfessional Psychology.
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