Oxytocin is often nicknamed the "love hormone" and frequently makes headlines in the press. But behind this idyllic image, the scientific reality is more complex. What does research really tell us about this molecule? Can love truly be reduced to a simple matter of chemistry?
A misleading nickname?
The association of oxytocin with love dates back to its discovery in the 20
th century. Oxytocin is a neuropeptide, a small protein that acts as a chemical messenger in the brain and many peripheral organs. It is notably responsible for uterine contractions triggering childbirth as well as the contraction of mammary glands during breastfeeding, promoting the mother-child bond. Oxytocin's role in this first filial love relationship was quickly overinterpreted to become the hormone of couples and romantic relationships.
Comparative biology actually warns us: less than 5% of mammals form monogamous pairs, yet all possess oxytocin. In voles, these small rodents often used as study models, monogamy or polygamy depends more on the distribution of oxytocin receptors in the brain than on the mere presence of this molecule.
So if oxytocin isn't the couple hormone, what is its true role?
The social bonding hormone above all
Rather than romantic love, current research tends to show that oxytocin is primarily the social bonding hormone. An essential distinction.
The extensively studied mother-child bond perfectly illustrates oxytocin's social role. Skin-to-skin contact stimulates its release in both mother and child, triggering a cascade of beneficial effects: reduced stress and anxiety, pain relief and enhanced mutual well-being.
"We go far beyond a role of love, eros, of oxytocin, but more filial, we're in the version of love as care for others," says Pierre-Marie Lledo, CNRS Research Director, UMR3571 - Genes, Synapses and Cognition (CNRS/Institut Pasteur).
Studies conducted at CNRS have explored this role of oxytocin in social motivation. Alexandre Charlet and his collaborators showed that in rodents, tactile interaction between two individuals activates specific neurons and promotes oxytocin release. This virtuous cycle maintains the desire for social interaction. Conversely, its absence can lead to progressive isolation. A particularly interesting research avenue in geriatrics, where social isolation is a major factor in depression and anxiety.
Therapeutic hopes... and limitations
Does oxytocin have therapeutic potential? This is what several research teams are exploring.
In the early 2010s in Lyon, Angela Sirigu's work showed that administering an oxytocin nasal spray could improve social interactions in children with Asperger's syndrome.
However, clinical application faces major obstacles. Oxytocin is a fragile small molecule: its half-life is extremely short (5 to 10 minutes) and it doesn't cross the blood-brain barrier. Its administration via nasal spray or blood injection therefore raises questions: how to explain the observed effects when the molecule can't directly reach the brain? This is the whole mystery of oxytocin.
To overcome these limitations, scientists are currently developing oxytocin receptor agonists, molecules that can mimic its effects while being more stable in the body. A hope for future medical applications.
Oxytocin and love at first sight: myth or reality?
Let's return to our starting point: can love at first sight be explained by oxytocin?
Studies on voles show that pair bonding involves several molecules: dopamine, serotonin, vasopressin and, of course, oxytocin. But these hormones act in different brain regions and at distinct moments in the attachment process.
Thus, oxytocin alone cannot be responsible for love at first sight.
If love were as simple as an oxytocin injection, a nasal spray would be enough to fall madly in love with the first person met on the street... which obviously isn't the case!
Alexandre Charlet, CNRS Research Director, UPR3212 - Institute of Cellular and Integrative Neuroscience (CNRS)
Love at first sight relies on a complex mix of sensory perception, cognition, emotions and social and cultural context. An unexpected encounter, an aesthetic that speaks to us, a voice that troubles us... So many elements that can't be reduced to a single molecule, but which induce the chemical reactions necessary for the emergence of this strong feeling.
A key molecule, but not a magical one
Far from being a simple "love hormone", oxytocin is an essential molecule for species survival. It encourages reproduction, parental care, social interactions, and even stress and pain management. A precious molecule, but whose action is much subtler than one might think.
Reducing oxytocin to a matter of love would be a mistake. Attachment, emotions and human relationships are far too complex to be explained by a single molecule. But by better understanding its role, new therapeutic avenues can be explored to better grasp the importance of social bonds in our well-being.
So, oxytocin, the love hormone? Not really. But a precious key that's there to make life easier for us and to bind us together.