Myth: The cuddle chemical

This week, Kat Arney has been getting up close and personal with the so-called "cuddle chemical".

Kat - It's been described as the 'hormone of love', and even 'nature's love glue' - a simple chemical that bonds mothers to their babies, is said to be responsible for keeping couples loved up, and has even been claimed to be able to make us all more generous, trustworthy and compassionate. We're talking about the molecule oxytocin, and there are research studies of varying size and quality showing that a lack of it might be to blame for problems such as alcohol or drug addiction, while a quick sniff of the stuff can keep men faithful, make you feel more sociable, and even help you lose weight.

But - sadly for anyone who's hoping that a simple squirt of oxytocin might be the solution to all their problems and help them snare the subject of their dreams - it's a bit more complicated than that.

Back in 2005, a trio of researchers published a paper in the journal Nature entitled "Oxytocin increases trust in humans", based on a small research study asking volunteers to play a game in which they had to trust each other, and were also given sniffs of the chemical. And while there's no doubt that oxytocin is a very interesting biological molecule, the full picture is more murky than moral.

Oxytocin is made in a part of the brain called the hypothalamus, and transported out across the whole body. Beyond doubt, we know that it plays important roles in birth, breastfeeding and parental bonding. And we also know that it's released in the brain and elsewhere in the body by non-pregnant people. But what's a bit more tricky to prove is exactly what it's doing, if and how it can change human behaviour, and whether it's acting alone or in concert with all the other chemicals and cues that feed into our thoughts, feelings and actions.

So what do we know?

Some of the strongest evidence for a role for oxytocin in romance doesn't come from humans at all, but from a certain species of prairie vole, Microtus ochrogaster, that pair bonds for life. And giving normally non-monogamous vole species doses of oxytocin and another so-called happy hormone, vasopression, switch them into monogamous behaviour. But, importantly, it's not enough just to dose voles with drugs to make them monogamous lovers - they need to spend time together too, at least six hours of hanging out together to feel bonded. But humans aren't voles, so what else do we know about how oxytocin might affect our brains and behaviours.

One small study of less than 100 participants, published in the Journal of Neuroscience, suggested that a sniff of oxytocin made men in long-term monogamous relationships keep a greater distance from an attractive woman (who wasn't their partner) than single ones.

Oxytocin has also been found to improve people's perception of their own personality, in turn making them more outgoing in social situations - again in a small study of in a small study of 100 people. It's been shown to counteract the feelings of drunkenness induced by alcohol and maybe even cut cravings for booze, and has also been shown to play a role in addiction. Furthermore, a preliminary report from a study of just 10 overweight or obese men reported at a meeting in April this year suggests that a sniff of oxytocin might help to improve their self-control around food.

It's certainly not all good news though. Giving people oxytocin can actually strengthen bad memories and increase anxiety, or make people oversensitive to the emotions of others.

Meanwhile a 2011 study with 280 Dutch volunteers showed that giving them oxytocin encouraged them to feel more negatively towards those perceived as outsiders, potentially encouraging racism, xenophobia and prejudice. It's also been linked with an increase in dishonesty in men, as well as other negatively-perceived feelings such as envy and schadenfreude. So much for the 'love chemical', if it only applies to loving people like you...

Another study showed that giving couples sniffs of oxytocin could help boost communication between them. It's clear that communication is key to good relationships, and even just talking with and touching each other can lead to oxytocin release in the brain. But can adding oxytocin jump-start the communication process and salvage a relationship on the skids? We don't know, because human love-lives are far trickier to unravel in the lab than simple cells or organisms.

There are also big differences between people that affect how they respond to oxytocin in different circumstances. Some of them are down to personality, others are genetic, and yet more come down to sex - men and women respond differently to the hormone.

Regardless of the conflicting scientific evidence, oxytocin's reputation as the love drug is problematic, because the reporting about its loved-up effects has now meant that it's possible to buy oxytocin on the internet, even though there's no good evidence that it's effective, safe for long-term use, or that it's even what it says on the bottle.

So what does oxytocin actually do, if it isn't fair to call it the 'love drug' or 'cuddle chemical'? And there's certainly no good evidence that giving people a whiff of oxytocin will make them fall in love, stop them from straying or make the world a better place - that's an awful lot to ask of a single molecule in the molecular maelstrom of our bodies and brains. It's probably safest just to say that it's a molecule that has an influence on our social interactions, but exactly how depends on who we are and our circumstances. And that's not something a quick squirt from a bottle of oxytocin can change, however much you want to believe the hormone hype.