‘Love’ hormone has a dark side

Oxytocin may accentuate social tendencies for good or ill

SAN ANTONIO — Oxytocin, a hormone with a rosy reputation for getting people to love, trust and generally make nice with one another, can get down and dirty, according to evidence presented on January 28 at the annual meeting of the Society for Personality and Social Psychology.

This brain-altering substance apparently amplifies whatever social proclivities a person already possesses, whether positive or negative, says psychologist Jennifer Bartz of Mount Sinai School of Medicine in New York City.

Previous work has shown that a nasal blast of the hormone encourages a usually trusting person to become more trusting (SN Online: 5/21/08), but now Bartz and her colleagues find that it also makes a highly suspicious person more uncooperative and hostile than ever.

“Oxytocin does not simply make everyone feel more secure, trusting and prosocial,” Bartz says.

These new results raise concerns about plans by some researchers to administer oxytocin to people with autism and other psychiatric conditions that include social difficulties, she adds.

Her team studied 14 people diagnosed with borderline personality disorder and 13 volunteers with no psychiatric conditions. Symptoms of borderline personality disorder include severe insecurity about relationships, fears of abandonment and constant, needy reassurance-seeking from partners.

Borderline personality disorder usually occurs in women, but Bartz’s sample included four men. Her group of healthy participants included seven men.

Members of each group played a computer game with an experimenter posing as a research volunteer. In each of three rounds, volunteers had to predict whether their partner would cooperate with them so that each player could make $6 or if the partner would leave the game in order to claim $4 alone.

Volunteers who suspected the partner of bad intent could leave the game early and claim $4 for themselves.

Borderline personality players of both sexes left the game early far more often after receiving an oxytocin nasal spray than after whiffing a placebo spray. Inhaling the hormone prodded their already high levels of hostile suspicion and depleted minimal reserves of trust, Bartz suggests.

Psychiatrically healthy players became more cooperative in the money game after getting oxytocin, relative to their placebo responses.

Nasally inhaling oxytocin also magnifies men’s memories of their mothers as being either supportive or not, Bartz says. Her team had 31 men fill out surveys on the quality of their relationships with their mothers up to age 16.

Those who described good maternal relationships remembered mom as substantially more caring and supportive after receiving oxytocin, compared with after inhaling a placebo spray. Those whose early home life had been troubled remembered mom as much less caring and supportive after oxytocin, versus placebo.

Bartz’s team initially described oxytocin’s two-sided influence on men’s maternal memories in the Dec. 14 Proceedings of the National Academy of Sciences.

These findings underscore that “oxytocin is not a love hormone; its effects vary in different people,” remarks psychologist Greg Norman of Ohio State University in Columbus.

Norman and his colleagues have found that oxytocin stimulates the heart to beat more in sync with the breathing cycle in people with healthy social lives, but not in people who report constant loneliness.

Other researchers have recently reported that oxytocin stimulates greater trust of members of one’s own ethnic group and greater suspicion of other ethnicities.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.