As February rolls in, thoughts of love inevitably take centre stage. With Valentine’s Day on the horizon, chocolates and flowers fly off the shelves as people seek to express affection for their "special someone." Love is often described as a fluttering in the stomach, a quickened heartbeat, and perhaps a touch of nervousness around someone attractive. But what triggers these physical reactions merely by seeing someone? Well, ask an endocrinologist and you would get a very literal answer: a cocktail of neuropeptides and neurotransmitters. The idea of love is much more philosophical in nature than scientific, but the feelings that love brings can be explained through a bit of chemistry. Dr. Helen Fisher’s team at Rutgers University in New Jersey hypothesised that humans have evolved three emotional systems that encompass the feeling of love, each with their own concoction of hormones to bring about a unique feeling. 

Feeling the Chemistry

The first emotional system involves basic biological desires shared by all living things: the need to reproduce. This is classified as lust, also referred to as the libido or the sex drive, and it is regulated by hormones travelling to the anterior pituitary, leading to the production of the sex steroids from the gonads (better known as testes and ovaries). These include testosterone and estrogen, which are both found in males and females despite typical stereotyping. These hormones subsequently trigger an uptick in libido, which is closely tied to the sensation of "sexual attraction" individuals experience, regardless of whether romantic feelings are present or not.

Love at First Sight

The discussion of romance leads to the second emotional system: attraction. This has been recognized as a separate system for a while despite how closely it can be associated with lust. The concept of sexual selection was introduced by Darwin and explains that despite the hormones that fuel sexual attraction, mammals are still selective with who they choose as their mates. Attraction as a whole is a complex subject, but there are some chemicals found in the brain that serve to explain those feelings often associated with love. 

Dopamine, a neurotransmitter produced by the hypothalamus, is widely recognized as the chemical released when we experience pleasure. It's strongly associated with feelings of euphoria, excessive energy, and sleeplessness, which can explain the "honeymoon stage" of new relationships where a couple just can't get enough of each other. Closely associated with dopamine is norepinephrine, also known as adrenaline. Their effects are largely the same, though norepinephrine is more involved in exhilaration and excitatory responses in the body, akin to the chemical involved in our body's fight or flight response. Phenylethylamine is another chemical responsible for inducing the exhilarating sensation of attraction, often associated with the "lovesick" feeling akin to butterflies fluttering in your stomach. Finally, low levels of serotonin can be attributed to this feeling of attraction as well, manifesting in insomnia and obsessive thinking, such as when you can't get that certain someone off your mind.

Long Lasting Love

Finally, attachment is the last emotional system associated with love and unlike the previous two, attachment isn’t exclusive to romantic love. This could include the love you feel for your friends and family, and is very characteristic of parent-infant bonding. Oxytocin and vasopressin, released in the central nervous system, are the hormones primarily responsible for these behaviours we experience but in different ways. Nicknamed the “cuddle hormone”, oxytocin promotes positive feelings during events leading up to bonding such as during sex, childbirth, and breastfeeding. Bonding is facilitated by oxytocin, but the need to protect those we have an attachment to is due to vasopressin. This hormone supports vigilance and other territorial or defensive behaviours, ensuring the safeguarding of those we have attachments to. 

Love, a concept too intricate and elusive to neatly define scientifically, remains a subject of ongoing exploration despite numerous attempts to understand its intricacies. While our hormones undoubtedly play a pivotal role in generating symptoms akin to "love sickness," ultimately, the decision of whom to bestow our affection upon lies within each individual.

Happy Valentine’s Day!