The Biology of Love

The Biology of Love


Love is a weird concept. It is something that is introduced to us the second we are born into this world and it is certainly something which is different for everyone. Some people believe that it doesn’t exist, but the fact of the matter is, through science, we can see that this phenomenon we call love really does exist all around us. Let’s break it down.


Emotions are reactions that human beings experience in response to events or situations or the physical and mental states brought on by neurophysiological changes. From what we know, there are six universal emotions, discovered by psychologist Paul Ekman, which are sadness, happiness, fear, anger, surprise,
and disgust. You may notice that love does not appear within the six. Well, an emotion classification system known as the wheel of emotions, discovered by Robert Plutchik, demonstrates how different emotions are blended together, much like how an artist mixes the primary colours to create more colours.

As shown above, we can see than a sensation of both Joy and Trust could equal the emotion of love.

It is important to understand that these emotions are subjective and another person’s anger may not be yours. Another person’s joy or trust may not be the same as yours and therefore, their perception of love is different. It is also rare that one feels the pure state of one of these emotions as being in situations where we have mixed emotions are all too common. For example, we might be excited to get married, but of course anxious for what may follow.

The three stages of love

Romantic love can be broken down into three main categories. Lust, Attraction, and Attachment. Lets break these down individually.

Lust. The sensation of requiring sexual satisfaction and stems from our evolutionary need to reproduce. The hypothalamus of the brain plays a big role in this, stimulating the production of the sex hormones, testosterone and oestrogen in the testes and ovaries respectively. Both hormones play a role in both men
and women and testosterone especially increases libido in both men and women, however men do have 40 times as much testosterone as women, which is thought to cause a more intense sex drive. Oestrogen does this to a lesser degree, however some women do report a higher sex drive around the time they ovulate.

Attraction. This stage involves Dopamine which is produced in the hypothalamus and is a ‘feel good hormone’, released during sex or spending time with loved ones. High levels of Dopamine and Norepinephrine are released during this stage and give rise to what we know to be the ‘honeymoon phase’ in the relationship. Attraction also results in the reduction in serotonin, a hormone known to be
involved in appetite and mood.

Let’s discuss the role of Pheromones and MHC in this stage. Pheromones are a chemical factor secreted by an individual with the intent to be received and trigger a social response by another individual of the same species. MHC (Major Histocompatibility Complex) acts similarly to Pheromones. They code for
proteins that recognise pathogens and influence mating preferences. Individuals with dissimilar MHC genes are more likely to produce offspring with stronger immune systems. This is associated with the idea that ‘opposites attract’.

Attachment. The predominant factor in long-term relationships. It mediates friendships, parent-infant bonding, and many other intimacies. Here, the hormones present are oxytocin, the ‘cuddle hormone’, and Vasopressin. Oxytocin is produced in the hypothalamus in large quantities during sex, breastfeeding,
and childbirth, activities which may not always be enjoyable, however are all precursors to bonding. Vasopressin is released as a result of attachment or social bonding, and interacts with the brain’s reward system, enhancing the rewarding aspects of attachment.

The Ugly side

Love can also often be accompanied by jealousy, erratic behaviour, and irrationality. The hormones responsible for the happy side of love also bring the downsides of love.

The same regions of the dopamine pathway which light up during attraction also light up when we binge eat or when drug addicts take cocaine. To put it simply, it is as if attraction is an addiction to another human being. We then face the battle of differentiating if our love is genuine or if we’re just chasing a
‘love high’.

With Oxytocin, it is pretty much the same story. Party drugs such as MDMA and GHB show that Oxytocin may be the hormone behind the feel-good, sociable effects that these chemicals produce within us. In extreme cases, these hormones can cause someone to act recklessly during different stages of the

Sexual arousal appears to turn off regions in our brain that regulate critical thinking, self-awareness, and rational behaviour, in short, making us dumb. If we aren’t careful, our love can transform into codependent or unrequited love, leading to anxiety, bad mood, sleep disturbances, unbalanced hormone levels, and changes to our normal behaviour.


Love, as simple as its introduced to us, is an extremely complex phenomenon with many different chemicals at play. It’s such a strong emotion that it has the ability to override our ways of thinking and how we act toward others. It’s a dangerous drug that we cannot control our intake of, no matter how hard we try.