When the Love Hormone Is Not So Cuddly
Studies on the use of oxytocin as a medicine have had some surprising results.
Posted June 11, 2025 | Reviewed by Monica Vilhauer Ph.D.
Oxytocin is often referred to as the “love hormone ” or “cuddle hormone”, because it promotes bonding and attachment – both between mothers and infants, and in adult romantic relationships .
As a consequence, oxytocin has been tested as a potential therapy for conditions associated with emotional or social detachment – most notably, autism spectrum disorders, postpartum depression , and schizophrenia.
An important advance for using oxytocin as a medicine was the discovery that nasal sprays could deliver a dose of oxytocin that gained access to the brain, causing changes in behaviour that could be measured experimentally. The prospects for therapy seemed very promising.
Unfortunately, this initial excitement has recently begun to wane, as results from controlled trials have revealed that the effects of oxytocin on human behaviour are more complex and varied than expected.
The action of oxytocin in the brain turns out to be much more subtle and sophisticated than just making cuddles feel good.
The name “oxytocin” roughly translates as “quick birth”, reflecting the fact that the hormone was first discovered as the driving force behind uterine contractions during labour. Oxytocin is released from the pituitary gland into the blood to stimulate delivery. It also causes the “let down reflex” during breastfeeding that initiates milk flow in response to suckling.
Oxytocin is therefore central to the mechanics of childbirth and infant care, but that’s not all it does. It’s also involved in the emotional bonding process between mother and child. As well as being released into the blood from the pituitary, oxytocin is also released from the hypothalamus back into the brain. Through this route, oxytocin regulates emotion , mood and behaviour.
Skin to skin contact causes oxytocin release in both mother and child, promoting feelings of security, affinity, and love. It helps synchronise levels of arousal, lower stress hormone levels, and stabilise emotional attachment.
Evolution is thrifty. It often replicates and redirects existing systems into new purposes, and oxytocin seems to be a good example of this principle. An attachment system for promoting infant development and survival was repurposed into a mechanism for promoting pair bonding in mating adults (Walum & Young 2018).
In socially monogamous species, oxytocin receptors are often present at high densities in brain regions associated with reward, pleasure, and sexual activity. As a consequence, mating promotes pair bonding. A specific partner becomes tightly linked with reward, at a neurochemical level, as dopamine and oxytocin are synchronously released during sex.
Much of our knowledge about how oxytocin regulates pair bonding comes from an unlikely source: the humble prairie vole. These little mammals form an unusually powerful bond. Release of oxytocin during mating imprints the partner as a primary attachment, a bond that lasts beyond a breeding season and even beyond the death of one of the pair.
Humans also practice social monogamy – certainly if you compare us to other primate species – and although the pattern of oxytocin receptors in our brains doesn’t exactly mirror the prairie vole, we have the same capacity for linking romantic attraction to euphoric reward. Perhaps the most striking example of this is limerence: an intense, obsessive, romantic infatuation with another person.
Evolution expanded oxytocin’s scope of operations from infant bonding to adult bonding, but it didn’t stop there.
Nasal spray delivery of oxytocin opened a new frontier in behavioural research. It became possible for researchers to dose people with oxytocin and measure the effects on their mood and behaviour. The results have been surprising (Yao & Kendrick 2025).
Despite the foundation of knowledge about oxytocin and infant-parent bonding, attempts to treat postpartum depression with nasal delivery have had weak and mixed results.
Similarly, while there is evidence that dosing with oxytocin can make a potential sexual partner seem more attractive, the effects of taking oxytocin for romantic attachment are also modest, complicated, and inconclusive.
Perhaps the most striking outcome of this research has been the discovery that the pro-social effects of oxytocin are much more wide-ranging and impactful than just intimate familial bonds.
Oxytocin increases trust between strangers in cooperative tasks. It promotes in-group loyalty and cooperation . It increases anxiety about social exclusion. It improves recognition of familiar faces and increases anxiety responses to negative facial expressions. It even increases trust in the opinions of authority figures.
Oxytocin is not just a snuggly love hormone. It acts as a high-level signal for directing attention to socially significant cues that carry both opportunities and risks. Oxytocin signals “social salience” and thereby helps us navigate the social environment by learning how to compete or cooperate with others effectively.
While these effects could be seen as functions of bonding raised to the level of a community, it’s also easy to see how they can promote tribalism and favoritism. After all, social interactions aren’t always about good feelings. Oxytocin doesn’t just make you feel tranquil and affectionate.
The future of oxytocin therapy
While we might have been hoping for quick wins with oxytocin therapy, we instead got a deeper understanding of how oxytocin actually works.
Oxytocin doesn’t directly activate specific neurons, it inhibits or augments signalling by the core neurotransmitter systems that drive our behaviour. It’s a tuning mechanism.
Sadly, snorting a dose of oxytocin that will end up both in the brain and in the bloodstream (with uncertain efficiency and timing) is not a sophisticated enough approach to selectively target a specific medical condition and get predictable benefits.
As if to underline this complexity and uncertainty, a recent study defied all expectations by reporting that deleting the gene for oxytocin receptors from our old friend the monogamous prairie vole did not prevent them from forming pair bonds (Berendzen et al. 2023). It seems that during development, alternative modulatory systems can somehow compensate for the loss of oxytocin signalling and recover the bonding process.
Social behaviour is rarely straightforward.
There’s still a lot more of the story to be discovered.
Walum, H., & Young, L.J. (2018) The neural mechanisms and circuitry of the pair bond. Nature Reviews Neuroscience. 19(11): 643-654.
Yao, S., & Kendrick, K.M. (2025). How does oxytocin modulate human behavior? Molecular Psychiatry. 30(4): 1639-1651.
Berendzen, K.M., et al. (2023) Oxytocin receptor is not required for social attachment in prairie voles. Neuron. 111(6): 787-796.
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Tom Bellamy, Ph.D., is a neuroscientist and honorary Associate Professor at the University of Nottingham, UK.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.