Medical: Oxytocin studies show hormone's dark side
Last Updated: 130 days ago
By LEE BOWMAN
Scripps Howard News Service
The cozy little hormone that makes new moms coo and couples cuddle isn't all sweetness and light. Oxytocin can also make hurt more intense and long-lasting.
Researchers have long known that the hormone is tied to romantic love and sexual orgasm as well as social bonding and well-being. It plays a role in fostering labor contractions and then helps new moms bond with and breast-feed their babies.
Animal studies have shown the hormone may help boost male monogamy by keeping the focus on one's mate. But another newly reported study of mice suggests oxytocin also plays an important role in making negative emotional memories more intense.
The activation of certain structures in the brain by oxytocin during a negative or stressful social experience like being bullied or tormented by a boss may make memories of that experience last long past the event itself and perhaps trigger fear and anxiety in the future, researchers at Northwestern University reported online in the journal Nature Neuroscience.
The studies involved putting mice in various settings where they experienced fear or aggression from other mice and measuring varied responses from those with extra oxytocin receptors, no receptors or mice with normal receptors.
The Northwestern scientists also discovered that the brain region responsible for these effects is called the lateral septum, a region that has the highest oxytocin levels in the brain and has high levels of oxytocin receptors across all species from mice to humans.
They note that understanding this dual function for the hormone is important, because earlier studies suggested it could be useful in treating anxiety, depression, even promoting social behaviors in people with autism. It appears that any treatments using doses of the hormone will have to take into account social context and other factors to get the best results.
Other recent studies have focused on the usefulness of oxytocin in fostering trust and overcoming social rejection.
One Canadian study from researchers at Concordia University published last month in the journal Psychoneuroendocrinology found varied responses to social rejection from students given a real or fake nasal spray dose of oxytocin, then put into a conversational setting in which they were given increasingly negative responses and eventually excluded.
Ninety minutes after taking the drug, participants answered questionnaires about their mood and levels of trust. Basically, students who felt worse about social rejection said they still felt more trusting after getting the hormone compared to those who got a placebo, while students who seemed to shrug off the social rejection reported no increase in trust after getting the hormone.
The researchers speculated that oxytocin may promote trust by dampening the "fear circuitry" of the brain while facilitating "social-approach" behaviors.
But an Australian study announced by researchers July 17 found that the nasal sprays of the hormone did not improve the symptoms of autism in a group of children. Other smaller studies had shown indications it might help.
Researchers from the University of New South Wales did a clinical trial with 38 boys between the ages of 7 and 16 diagnosed with autism. Half were given a spray with the hormone over four days, the rest a placebo spray.
Assessments with parents were done before treatment, three times during the treatments, immediately afterward and after three months, measuring things such as eye contact, responsiveness, speech, positive body language and recognition of facial emotions.
The researchers concluded that oxytocin did not significantly improve emotional recognition, social interaction skills, repetitive behaviors or general behavioral adjustment. They speculate that many children with autism may have impaired oxytocin receptor systems, but that there still might be some for whom supplements might be helpful.
The Australian has been accepted for publication in a future issue of the Journal of Autism and Developmental Disorders.
Still another oxytocin spray study reported last month involved giving single doses to adults with chronic migraine attacks. After two to four hours, 64 percent of those who got the hormone reported substantial reduction in pain, compared to 27 percent of those who got a placebo.
Researchers at Stanford University said the intranasal delivery of the hormone allows it direct access to the part of the nervous system that is involved in migraine and channels all pain information from the head. The study was presented earlier this month at the International Headache Conference in Boston.
(Contact Scripps health and science writer Lee Bowman at BowmanL@shns.com. Distributed by Scripps Howard News Service, www.shns.com.)
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