Imagine a molecule that underlies the virtues that glue societies together. Imagine that it brought out the better angels of our nature with just a sniff and could “rebond our troubled world.” Imagine that it was the “source of love and prosperity” and explained “what makes us good and evil.”

Well, carry on imagining. This is a story about oxytocin, and oxytocin is not that molecule.

You could be forgiven for thinking otherwise. For almost a decade, this simple hormone has been relentlessly hyped as a one-ingredient recipe for a utopian society. This molecular high-five, which is released when we hug, tweet, dance and orgasm, has been linked to trust, cooperation, empathy and a laundry list of other virtues. Io9 anointed oxytocin “the most amazing molecule in the world.” Other writers have added alliteration to breathlessness and billed oxytocin as the “cuddle chemical,” “hug hormone” and “moral molecule.”

That last one adorns the cover of a new book by Paul Zak, the self-described “Dr. Love” who hugs everyone he encounters. He was recently profiled by Oliver Burkeman in the Guardian, the latest episode in a long flirtation with the media in which he regularly expounds on oxytocin’s supposed wonders. You can see why journalists love him. He’s charming, handsome, and infused with that “big ideas” aesthetic that TED so adores. When he delivered his own TED talk in July 2011, he unabashedly claimed that he had found the molecule behind why we’re moral.

The problem with the moral molecule idea is that it turns science — messy, complex, frustrating as it is — into a tidy fable. It’s a bit too … well … TED-dy. It not only tells people what they want to hear but also makes them feel delightfully subversive for understanding the secret simplicity of the world. One molecule underlies morality? Seems far-fetched, but not impossible. Hugs can change the world? Everyone likes hugs! We can counter our imps of the perverse by breathing in the right molecule? Yahtzee!

But these bold words are not backed by equally bold evidence. Oxytocin hype might be storming the heavens, but oxytocin science is still finding its footing. Early studies certainly bathed the hormone in a shiny glow, but later ones uncovered a darker side. The “love hormone” fosters trust and generosity in some situations but envy and bias in others, and it can produce opposite effects in different people.

A more nuanced view of oxytocin is coming to light — one that’s inconsistent with the simplistic “moral molecule” moniker.

Oxytocin is made in a part of the brain called the hypothalamus, but it influences the entire body. It spikes when we’re sexually aroused, makes wombs contract before birth and triggers the release of breast milk. For decades, animal studies have shown that oxytocin is important for social interactions. If you block the hormone, monogamous voles become more promiscuous and ewes neglect their newborn lambs.

Then, in 2005, Michael Kosfeld and Markus Heinrichs asked volunteers to play a game of trust after sniffing either oxytocin or a placebo. (Zak, often solely credited for this work, was the third author on the paper.) The volunteers had to decide how much money to invest in an anonymous partner, who could reimburse them later or keep all the money. Despite the potential for betrayal, the oxytocin-sniffers entrusted more money to their partners than those who sniffed a placebo.

Heinrichs downplays the hype around a “good hormone,” but his study kicked off an oxytocin fever. Various research groups showed that oxytocin sniffs can make people more trusting, generous, cooperative, sensitive to the emotions of others, constructive in their communications, and charitable in their judgments of others. Zak continued to link oxytocin with trust and generosity, although John Conlisk, an economist from the University of California at San Diego, later analyzed those papers and suggested that “some conclusions are too enthusiastic.”

Other results would further discolor the rose-tinted view. Some scientists have found that oxytocin boosts envy and schadenfreude, as well as favoritism toward one’s own clique. In one experiment, volunteers who played a game with people they knew were more cooperative after a noseful of oxytocin, while those who played with anonymous strangers became less cooperative.

Jennifer Bartz, from the Mount Sinai School of Medicine, has found several responses that depend on a person’s mindset. She showed that socially secure people remember their mothers in a more positive light after inhaling oxytocin, while anxious ones remember mum as less caring and more distant. Along similar lines, she showed that oxytocin hinders trust and cooperation among people with borderline personality disorder.

These nuances didn’t come out of the blue. When Bartz looked at the early oxytocin studies more closely, she found that around half of them showed that the hormone enhanced positive behavior only in certain situations or individuals.

Sue Carter, who did much of the early oxytocin research with animals, views oytocin as part of an adaptive system that allows us to coordinate our behavior with our social situation. It’s a system that acts against the background of our histories and emotions.

The problem with oxytocin research is that too many people have been focusing on cataloging what it does (at least in some situations), rather than how it works. Say I’m new to computers and install my first Web browser. Suddenly, I can talk to friends, check train times and buy books. Web browsers look like a pretty sweet thing. Then I discover Chatroulette and things are not sweet any longer. And none of this tells me anything about the existence of the internet, servers, code and so on. I know what Web browsers can do, but not how they work.

This is the stage we’re at with oxytocin, and it’s the problem that Bartz and others want to crack. They already have some good ideas. Maybe oxytocin is a motivator that drives us to seek out social interactions. That would explain why it improves trust in some situations but drives bias and favoritism in others. More likely still, oxytocin could be a spotlight that draws our attention to social cues, making them more noteworthy. If we are naturally sociable, that’s a boon. If we are anxious, oxytocin only exacerbates the things that make us nervous.

These hypotheses are up for testing. Either or both of them might be correct, but neither fits with the idea of a single molecule that’s the seat of morality. The truth, as they say, is a bit more complicated than that.

Why does any of this matter? Because the hype around oxytocin hurts and exploits vulnerable people. The hormone’s reputed ability to fix social ills has drawn the attention of parents whose children have autism, depression or other conditions characterised by social problems. Many groups are looking to use oxytocin to ease those conditions, but always with great caution.

Heinrichs, for example, is running a trial to see if oxytocin can help people with borderline personality disorder, when used alongside normal therapy. “If you sit at home with a social phobia and a prescribed nasal spray, the only effect you’d get would be a dripping nose,” he told me last year when I spoke to him for a New Scientist story.

But some people aren’t going to wait. Many of the scientists I have spoken to have been approached by parents who had bought oxytocin from the Internet and were using it to treat their relatives. “That’s very worrying,” says Carter. “There hasn’t been a single published study on the use of oxytocin in young children, and we have no knowledge of the long-term consequences.”

In many ways, oxytocin epitomizes what happens when enthusiasm, salesmanship and optimism runs ahead of evidence and careful experimentation. The true moral of the moral molecule may be that ideas that are too cleanly packaged are probably just fragments.