Neurotransmitters and Attachment: The Chemistry Behind Human Bonding

By Katie Caygill Pocock (MSc. Clinical Neuropsychiatry, BSc. Psychology with Neuroscience), with contributions from Dr. Pascal Vrticka, Professor of Psychology at the University of Essex.

“We don’t get to choose who we love” has been repeated many times – it’s common to feel a sense that we don’t have control over the people we develop feelings for. Perhaps we believe that it’s down to fate, or that our feelings are determined under the influence of a cocktail of brain chemicals. But how true is this, really?

Although it sounds like a heavy topic, you have probably already heard of all the key players we’ll be talking about today. At the end of this article, you’ll have a clear idea of what happens in the brain when you’re in love, how it’s shaped by your attachment, and how you can use this to support your work towards a more secure attachment style.

How The Body Talks

First, there are 2 important kinds of chemicals you need to know about: neurotransmitters and hormones.

Neurotransmitters send messages in the brain. They act very quickly, so the cause-and-effect is immediate. When you take the first sip of a crispy cold drink on a hot day, your brain releases dopamine straight away to tell you “this feels good, do it more” – this is an evolutionary mechanism designed to keep us doing things that keep us alive, like staying hydrated.

Hormones send messages all over the body. They have a much slower reaction time, so their effect takes longer to be noticeable and can build up slowly over time. When you feel stressed, a cascade of messages results in production of the hormone cortisol. If stress is consistently high, cortisol continues to build up, affecting multiple systems (e.g. digestive, cardiovascular, nervous). Removing the source of stress doesn’t immediately remove the cortisol, and the body can feel its impact for a while.

The Multi-System Reality of Neurotransmitters and Hormones

Many chemicals can be both neurotransmitters and hormones, depending on where they’re acting. Examples include dopamine, serotonin, and oxytocin. If they’re sending instant messages in the brain, they’re acting as neurotransmitters, but if they’re sending long-term signals around the body, they’re acting as hormones.

Crucially, the blood-brain-barrier prevents most molecules from crossing from the bloodstream to the brain and vice versa, so serotonin produced in the gut, for example, doesn’t directly increase serotonin levels in the brain.

Neurochemicals can also act differently depending on where they are – sometimes, the same chemical can bind to different receptors, and the consequence depends on what kind of receptor it binds to. All this to say that our brains are complex machines, and it’s not as simple as one chemical producing one outcome.

Now that you know how neurotransmitters and hormones actually work, we can take a look at the chemical processes involved in love and attachment.

What Happens in Your Brain When You Fall in Love?

When relationships progress, falling in love happens twice: the initial attraction produces feelings of attraction and the desire to be close, and as closeness grows, we build long-term attachments. These processes look surprisingly similar in terms of their neurochemical make-up, but they recruit different brain mechanisms.

Studies have suggested that all kinds of neurochemicals play a role in both kinds of romantic attraction, including serotonin and vasopressin – but love scientist Dr. Adam Bode argues that there are only 3 main “love chemicals” we have direct evidence for: dopamine, oxytocin, and endogenous (meaning they’re made by the body) opioids, like endorphins.

This doesn’t mean that those other neurochemicals have no association with love and attachment, but that the brain’s networks are vast and complex and we don’t have strong evidence that they’re as closely linked to love and attachment as we think.

Dopamine: Why Love Feels Good

Dopamine is implicated in learning and motivation; it drives us to do things that feel good by giving us a sense of reward². Usually, these things are associated with evolutionary survival benefits, like eating good food and accomplishing tasks, but activities like gambling and gaming also stimulate dopamine rewards – which is why we can find ourselves spending much longer than we intended to, or even realized we were, on these activities.

When we’re interested in or in love with someone, just seeing their face gives us a dopamine reward³. This drives us to interact with them more and more.

Oxytocin: The Bonding Chemical

Oxytocin is famously “the love hormone”, earning its name for its role in prosocial behavior and bonding – but it’s also a neurotransmitter, and it has a broader range of social functions and some non-social ones. For instance, oxytocin regulates aggression and parent-child bonding, appears to inhibit memory, learning, and stress, and may also play a role in eating and pain perception⁴.

Speaking to The Attachment Project, Dr. Pascal Vrticka, Senior Lecturer at The University of Essex, says:

“Many studies found oxytocin to have opposing and apparently anti-social effects. For example, oxytocin administration increased dishonesty/lying and the inclination for aggression, and made more insecure-anxiously attached adults remember their mothers as less caring and close. […] Overall, the currently available evidence and theory suggest that oxytocin certainly can be a ‘love hormone’ – especially within romantic and parent-child relationships that provide safety and help with stress management. However, we must not forget that oxytocin has many other functions that can have very different and even opposite effects.”

Like dopamine, oxytocin as a neurotransmitter appears to be stimulated by interacting with attachment figures, strengthening our associations between those relationships and experiencing positive feelings.

The Perfect Couple: Dopamine and Oxytocin

Dopamine and oxytocin each play a role in attachment formation on their own, but together, they create the strong bonds we know as attachments⁵.

In certain brain areas, dopamine and oxytocin neurotransmitter receptors are packed in together. When they fire at the same time, they each strengthen the other. This is the magic of attachment bonding – when we experience dopamine and oxytocin firing together, in response to the same person over and over, we learn to associate that person specifically with both reward and a sense of safety; one without the other creates a good relationship, but not a strong attachment.

Love at First Sight: Initial Attraction

The brain’s striatum, a network of structures linked to core functions of motivation and movement, is full of receptors for dopamine, oxytocin, and endorphins – suggesting these neurotransmitters are extra-active here. In the initial stages of a relationship, there’s high activity in the striatum’s nucleus accumbens, which is associated with that rapid sense of reward and pleasure from positive interactions⁵.

As dopamine and oxytocin fire together in the nucleus accumbens, we learn: this person makes me feel good, and I should stay close to them. This is the kind of connection that feels new and exciting, sometimes called the honeymoon phase – and, as enjoyable as it is, some changes need to happen in the brain to create a stable, deeper bond.

Brain Changes in Long-Term Attachment

As the attachment deepens, the firing between dopamine and oxytocin moves into another part of the striatum called the caudate, further towards the back of the brain. This brain area is associated with familiarity and predictability, in line with the way our attachment bonds move from pursuit and novelty to comfort and stability.

The Supporting Role of Endorphins

Another neurotransmitter system, beta-endorphin (β-endorphin) is also found abundantly in areas associated with reward and motivation, and has been found in high levels in people in early stage relationships¹. β-endorphins reduce pain and improve mood, and you might have heard them credited for the mood boost we get from exercising⁶.

Neuroscientists have suggested that endorphins, dopamine, and oxytocin all work together to both form and maintain attachment bonds – and the way they work adapts depending on whether you’re forming an initial attachment or sustaining a deeper connection.

How Neurotransmitter Profiles Differ by Attachment Style

Dr. Vrticka touched on how neurotransmitters might behave differently in people with different attachment styles. What else does research show?

According to Dr. Vrticka’s own research, we see different activation in those reward circuits in response to social stimuli depending on your attachment style⁷. A smiling face usually activates the reward pathways, but this effect was dampened in those with avoidant attachments. On the other hand, we show activation in the amygdala, the brain’s threat-detection center, when we see an angry face. Higher activation in this brain area was related to higher attachment anxiety.

Studies have also found differences in genes for neurotransmitter receptors: attachment anxiety was associated with variations of a dopamine receptor gene, and attachment avoidance was associated with variations of a serotonin receptor gene⁸. Notably, there was no association found between attachment style and an oxytocin receptor gene.

If the genes for our receptors are different, then the receptors might function in slightly different ways – perhaps they are more or less sensitive, altering the effects of those neurotransmitters. More research is needed to understand the effects of these findings.

From Childhood to Adulthood: How Early Care Shapes Your Neurochemistry

As children, we experience bio-behavioral synchrony with our caregivers: when we’re close with someone, our behaviors and biological markers, like breathing rate and brain activity, can synchronize.

Dr. Vrticka predicted that higher synchrony between infants and primary caregivers would be linked with attachment security. However, his research showed an interesting contradiction.

As described by Dr. Vrticka in a research interview for The Attachment Project:

“Our findings revealed that those mother-child dyads in which mothers were classified as insecure (versus secure) in their attachment representations showed increased interpersonal neural synchrony. We therefore think that insecure attachment representations in mothers may make it harder for the mother-child dyad to cooperate effectively and mutually, with more cognitive effort and attention needed from both interaction partners. […] A secure attachment bond, especially between children and their parents, should therefore not be understood as a bond within which there always is high synchrony, but rather an optimal amount of synchrony depending on the specific context and individuals involved.”

In this way, we can see how your infant attachments might lead to neurochemical changes. However, we don’t yet know what these changes might be. Further, your brain is very malleable – neuroplasticity is the mechanism by which your brain adapts to its circumstances. When you use receptors more often, your brain makes more of them; when you stop using them, your brain “prunes” them back. Neuroplasticity is how the repeated firing of dopamine and oxytocin together strengthens the connection.

Therefore, even if we did find neurochemical differences in infants depending on their attachment styles, this doesn’t mean that these differences are set in stone. Just as your attachment style can change with time and experience, so can your neurochemistry, to an extent – remember that genetics also play a role.

Conclusion

Falling in love is an amazing, complex process, and we still don’t completely understand what happens in your brain when you’re in love. However, scientists have found that the interactions between 2 neurotransmitters, dopamine and oxytocin, are key to both the excitement of attachment formation and the stability of deeper attachment bonds, with a possible supporting role from endorphins as the body’s natural mood-boosters.

Other neurotransmitters and hormones like serotonin, vasopressin, and norepinephrine are involved in love and attachment, but the brain and body are such intricate networks that it’s difficult to untangle the exact biological processes. For many, falling in love feels like magic – although evolutionary neurobiology takes away a little mystery, perhaps the complexity and intricacy of love in the brain is a magic of its own.

FAQs About Neurotransmitters and Attachment

Is oxytocin the love hormone that causes secure attachment?

Dr. Vrticka says that oxytocin could reasonably be called a “love hormone”, but we need to acknowledge that it also has other effects related to social processing, sometimes in opposition to what we expect.

Can oxytocin make you fall in love?

Oxytocin can enhance bonding and feelings of attachment, but it doesn’t make you fall in love all on its own.

What hormone makes you fall in love?

As neurotransmitters, oxytocin and dopamine fire together when we form an attachment bond: dopamine makes it feel good, and oxytocin makes it feel comfortable.

Can you heal attachment through neuroplasticity?

In theory, neuroplasticity can help you to heal attachment insecurity by altering your neurochemistry. However, we need more research to understand the patterns and stability of neurotransmitters in attachment processes.

References

1. Bode A. Romantic love evolved by co-opting mother-infant bonding. Frontiers in Psychology. 2023 Oct 17;14:1176067.
2. Berke JD. What does dopamine mean?. Nature neuroscience. 2018 Jun;21(6):787-93.
3. Aron A, Fisher H, Mashek DJ, Strong G, Li H, Brown LL. Reward, motivation, and emotion systems associated with early-stage intense romantic love. Journal of neurophysiology. 2005 Jul;94(1):327-37.
4. Lee HJ, Macbeth AH, Pagani JH, Young 3rd WS. Oxytocin: the great facilitator of life. Progress in neurobiology. 2009 Jun 1;88(2):127-51.
5. Feldman R. The neurobiology of human attachments. Trends in cognitive sciences. 2017 Feb 1;21(2):80-99.
6. Dalayeun JF, Nores JM, Bergal S. Physiology of β-endorphins. A close-up view and a review of the literature. Biomedicine & pharmacotherapy. 1993 Jan 1;47(8):311-20.
7. Vrtička P, Andersson F, Grandjean D, Sander D, Vuilleumier P. Individual attachment style modulates human amygdala and striatum activation during social appraisal. PloS one. 2008 Aug 6;3(8):e2868.
8. Gillath O, Shaver PR, Baek JM, Chun DS. Genetic correlates of adult attachment style. Personality and Social Psychology Bulletin. 2008 Oct;34(10):1396-405.