Cupid’s chemical addiction – the science of love

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When Bryan Ferry and Roxy Music sang that “Love is The Drug” in their 1970’s hit they weren’t far from the truth. And when Haddaway asked the world “what is love?” in 1993, he was pondering the same thing that has puzzled scientists in fields ranging from anthropology to neuroscience for decades. 

Few things feel as effortless as the early stages of “true love” or the love felt by a mother for her child, but the reality is rather more complex, a pantomime of hormones and complex physiological interactions that make it a little wonder of the world. It turns out the science behind love is both simpler and more complicated than we might think.

The science responsible for us falling in love is often sensationalised, and as with many things in science we don’t yet know enough to draw firm conclusions about every piece of the puzzle, let alone put the puzzle together. What we do know, however, is that much of love can be explained by our biochemistry.

So, if there’s really a “formula” for love, what is it, and what does it mean? Where does love reside? What triggers it? And what’s really going on in our minds and bodies when we fall “head over heels”?

According to one of the best-known researchers on the topic, Dr. Helen Fisher, Senior Research Fellow, at The Kinsey Institute, Indiana University, and a Member of the Center For Human Evolutionary Studies in the Department of Anthropology at Rutgers University, when it comes to love, we are at the mercy of our biochemistry. Fisher says that romantic love can be broken down into three categories: lust, attraction, and attachment - each stage aided by a different set of hormones.


Lust is regarded by some Christian teachings as one of the seven deadly sins, a vice leading people down the path to misdeeds and moral corruption. German philosopher Schopenhauer wrote that “lust is the ultimate goal of almost all human endeavour, exerts an adverse influence on the most important affairs, interrupts the most serious business, sometimes for a while confuses even the greatest minds”. Lust according to Fisher though is integral to the formation of romantic love, driven by the desire for sexual gratification. The evolutionary basis for this stems from our need to reproduce, a need shared among all living things. Through reproduction, organisms pass on their genes, and thus contribute to the perpetuation of their species. Lust appears to be a natural part of living existence.

The brain's hypothalamus plays a big role in this, stimulating the production of the sex hormones testosterone and oestrogen from the testes and ovaries. While these chemicals are often stereotyped as being “male” and “female,” both play a role in men and women. Testosterone increases libido in just about everyone. The effects are less pronounced with oestrogen, but some women report being more sexually aroused around the time they ovulate, when their oestrogen levels are at their highest.


Attraction appears to be a distinct, though closely related, phenomenon. While we can certainly lust for someone we are attracted to, and vice versa, they can occur independently of one another. Attraction involves the brain pathways that control “reward” behaviour, which partly explains why the beginning of a romantic relationship can feel so exhilarating. People “in love” experience a range of intense feelings, such as intrusive thoughts, emotional dependency and increased energy, especially in the early phases of the relationship.

Numerous brain regions, particularly those associated with reward and motivation, are activated by the thought or presence of a romantic partner. These include the hippocampus, hypothalamus, and anterior cingulated cortex. When these areas are activated they may serve to inhibit defensive behaviour, reduce anxiety and increase trust in the romantic partner. At the same time areas such as the amygdala and frontal cortex are deactivated in response to romantic love, a process which may function to reduce the likelihood of negative emotions or judgement of their partner.

Brain activation in response to a romantic partner both rewards social interaction and impedes negative responses. How much the brain is activated during the early stages of a romantic relationship seems to influence both our own well-being and the extent to which the relationship is a success or failure. It's the difference between using the brain in our heads vs the "brain" in our pants from the lust phase.

Dopamine, produced by the hypothalamus, is a particularly well-publicised player in the brain’s reward pathway – it’s released when we do things that feel good to us. In this case, these things include spending time with loved ones and having sex. High levels of dopamine and a related hormone, norepinephrine, are released during attraction. These chemicals make us giddy, energetic, and euphoric, even leading to decreased appetite and insomnia – which means you actually can be so “in love” that you can’t eat and can’t sleep. In fact, norepinephrine, also known as noradrenalin, may sound familiar because it plays a large role in the fight or flight response, which kicks into high gear when we’re stressed and keeps us alert. Brain scans of people in love have actually shown that the primary “reward” centres of the brain fire like crazy when people are shown a photo of someone they are intensely attracted to, compared to when they are shown someone they feel neutral towards (like a work colleague or an old high school acquaintance).

Finally, attraction seems to lead to a reduction in serotonin, a hormone that’s known to be involved in appetite and mood. Interestingly, people who suffer from obsessive-compulsive disorder also have low levels of serotonin, leading scientists to speculate that this is what underlies the overpowering infatuation that characterizes the beginning stages of love.


Attachment is the predominant factor in long-term relationships. While lust and attraction are pretty much exclusive to romantic relationships, attachment mediates friendships, parent-infant bonding, social cordiality, and many other intimacies as well. Romantic love appears to be universal, but the extent to which romantic or sexual love forms an important part of long-term relationships may vary. For example, only 4.8% of Australian university students report that they would marry without romantic love compared to over 50% of those in Pakistan. 

The two primary hormones here appear to be oxytocin and vasopressin, the hormones most closely associated with romantic love. While men and women are both influenced by oxytocin and vasopressin, women are more sensitive to oxytocin and men are more sensitive to vasopressin. These hormones act on numerous systems within the brain and receptors are present in a number of brain areas associated with romantic love. In particular, oxytocin and vasporessin interact with the dopaminergic reward system and can stimulate dopamine release by the hypothalamus.

Oxytocin is often nicknamed “cuddle hormone” for this reason. Like dopamine, oxytocin is produced by the hypothalamus and released by the pituitary gland in large quantities during sex, breastfeeding, and childbirth. This may seem like a very strange assortment of activities – not all of which are necessarily enjoyable – but the common factor here is that all of these events are precursors to bonding. It also makes it pretty clear why having separate areas for attachment, lust, and attraction is important: we are attached to our immediate family, but those other emotions have no business there.

Researchers have often studied the influence of oxytocin and vasopressin in non-human animals such as the prairie and montane voles. It is clearly documented that prairie voles (which form monogamous lifetime relationships known as pair-bonds) have much higher densities of oxytocin and vasopressin receptors than the promiscuous montane voles, particularly in the dopamine reward system. When the release of oxytocin and vasopressin is blocked, prairie voles become promiscuous. Together, these findings highlight the manner in which hormone activity may help or hinder the formation of a close relationship.

Too much of a good thing

This all paints quite the rosy picture of love: hormones are released, making us feel good, rewarded, and close to our romantic partners. But it’s not that easy. Love is often accompanied by jealousy, erratic behaviour, and irrationality, along with many other less-than-positive emotions and moods. Our cocktail of love hormones is also responsible for the downsides of love.
Dopamine, for instance, is the hormone responsible for the vast majority of the brain’s reward pathway – and that means controlling both the good and the bad. The dopaminergic pathways activated during romantic love create the rewarding pleasurable feeling we know and, well, love. But the pathways are also associated with addictive behaviour, not unlike the obsessive behaviour and emotional dependency often observed in the initial stages of romantic love. We experience surges of dopamine for our virtues and our vices. In fact, the dopamine pathway is particularly well studied when it comes to addiction. The same regions that light up when we’re feeling attraction light up when drug addicts take cocaine and when we binge eat sweets. For example, cocaine maintains dopamine signalling for much longer than usual, leading to a temporary “high.” In a way, attraction is much like an addiction to another human being. 

The story is somewhat similar for oxytocin, where too much of a good thing can be bad. Studies on party drugs such as MDMA and GHB show that oxytocin may be the hormone behind the feel-good, sociable effects these chemicals produce. These positive feelings are taken to an extreme in this case, causing the user to dissociate from their environment and act wildly and recklessly. And oxytocin’s role as a “bonding” hormone appears to help reinforce the positive feelings we already feel towards the people we love. We become more attached to our families, friends, and significant others, when oxytocin is working in the background, reminding us why we like these people and increasing our affection for them. This is a good thing when it comes to monogamy, but such associations are not always positive. For example, oxytocin has also been suggested to play a role in ethnocentrism, increasing our love for people in our already-established cultural groups and making those unlike us seem more foreign. So, like dopamine, oxytocin can be a bit of a double-edged sword.

And finally, what would love be without embarrassment? Sexual arousal, but not necessarily attachment, appears to turn off regions in our brain that regulate critical thinking, self-awareness, and rational behaviour, including parts of the prefrontal cortex. In a nutshell, love makes us dumb and makes us do stupid things we often regret.

So Bryan Ferry was right, love is a kind of drug, and there is sort of a “chemical formula” for it. But there are many questions left unanswered, and it’s not just the hormone side of the equation that’s complicated. Love can be both the best and worst thing for you. It can be the thing that gets us up in the morning, or what makes us never want to wake up again. And why do we feel lust and attraction for one person but not another? In the end, everyone is capable of defining love for themselves. And, for better or for worse, if it’s all hormones then maybe each of us can have “chemistry” with just about anyone.

Happy St. Valentine’s Day!