How to have good chemistry with your partner (from a neurological perspective)

The chemistry of love

February 14th, 2023

Loren Meehan

Romance between two people should of course be based on one’s emotions and comfort with their significant other, but have you ever wondered what causes the emotions you feel when you see your crush, or why your significant other feels romantic/sexual attraction to you?

There are many misconceptions about human attraction. Humans do not give off pheromones, or do but to a negligible effect [1], we do not feel love as a singular chemical action, there is no “formula” for love.

What is love (baby don’t hurt me)

Your feelings towards another can be broken down into 3 components. Attraction, Lust, and Attachment [2]

1. Attraction is your romantic feelings towards another person, crushing on someone, liking someone for their personality, feeling good when the other person is around.

It’s important to remember that attraction does not work the same in everybody, and there are many individuals who don’t experience the attraction component, or only experience it for a specific close individual. Humans are complex and our brain and hormone signaling systems especially. These concepts cannot be applied to everyone, this article is only addressing the statistical mode of human expression.

1. Lust is your sexual attraction towards another person. Lust does not necessarily need attraction or attachment and is an involuntary reaction. Once again, these concepts do not apply to everyone.

1. Attachment is your desire to stay with someone. It’s what turns a fling into a long term relationship, and is an important component of non-romantic friendships as well.

How do these components work?

Click this link for a TLDR if you don’t care about the biological details

Each of these 3 components are attached to an associated hormone cascade, all starting with the hypothalamus, which is the gland in the brain that mediates emotion (among other things) [3].

The first component of love is Attraction

Attraction causes sensory inputs to trigger the hypothalamus, but stays within the brain, inhibiting dopamine and norepinephrine reuptake, the prefrontal cortex, and increasing serotonin reuptake. [7]

That sentence contained a lot of words that might be confusing, let me explain some terms.

What does reuptake mean?

Your brain transmits signals through chemicals called neurotransmitters (dopamine, norepinephrine, and serotonin are all neurotransmitters). Neurotransmitters sit at the end of the tail like part of the nerve cell (axon) that attaches to other neurons, called the axon terminal. When a signal reaches the axon terminal, the neurotransmitters travel through a space called the synaptic cleft, into the next nerve cell’s synapse, its signal input site. When the brain wants to decrease the concentration of a given neurotransmitter, it releases Monoamine transporters, or MATs, which bind to the neurotransmitter and carry them back to the axon terminal. Reuptake describes this process of using MATs to reduce neurotransmitter levels in the nervous system. When reupatke in inhibited, through enzyme inhibitors, it increases the levels of a given neurotransmitter in the nervous system [5].

Now what do the individual neurotransmitters involved in attraction do in the brain?

Dopamine is traditionally considered the reward chemical in the brain, but it’s an essential hormone that has many effects, regulating motor control, motivation, interest, pleasure, and reward [6]. This is why love can have an almost addictive aspect, and cause such a strong reaction in a breakup [7]. Dopamine’s effect on motor function and speech is why dopamine reuptake inhibition is often prescribed for psychotic disorders [8].

During attraction, dopamine is why you would do things for your partner that you would not put in the effort for in others, why early love causes a “high”, and why one can feel euphoric around their partner [7].

Norepinephrine is a chemical that might sound familiar through its less common name, noradrenaline. As the name suggests, norepinephrine mediates fight or flight responses in the body [9]. norepinephrine reuptake inhibition is often prescribed to help with anxiety [10].

During attraction, norepinephrine is what causes the nervous feeling around your partner, as well as skin blush, clammy skin, and increased body temperature, as it raises blood pressure and heart rate, increasing blood flow to the checks and sweat production to deal with the excess heat created [11].

The last neurotransmitter is serotonin. Serotonin is known as the mood regulating chemical of the brain, and low levels of serotonin have been linked to depression and other mood disorders [12]. Serotonin serves a load of roles in the body, such as mood, cognition, hunger, reward, learning, and memory in the brain, and vasoconstriction (Constriction of blood vessels), platelet coagulation (wound healing), vomiting, and intestinal peristalsis in the body [13].

Unlike the previous two neurotransmitters, attraction decreases serotonin levels in the brain. The reason for this is not exactly clear, but links between low serotonin levels and Obsessive Compulsive Disorder might suggest that the increased serotonin reuptake is what causes the infatuation you feel towards your partner [14].

The last aspect of that first sentence was that attraction inhibits the prefrontal cortex, which is the reason and decision making center of the brain. This explains why you might make irrational decisions around your partner that you would not do otherwise [15].

The second component of love is lust

Lust is your sexual desire towards your partner and is mediated by a more complex hormone cascade than earlier (that I will not be explaining in detail), called the HPG axis, short for the Hypothalamus Pituitary Gonadal axis. Sensory inputs trigger the hypothalamus, which triggers the pituitary gland, doing many things that I will not be explaining, but primarily triggering the gonads [16], which are your ovaries or testes depending on one’s sex. In the gonads is the gonadotropin releasing hormone (GNRH), which triggers steroidogenesis, in which the production of progestins (such as progesterone), corticoids and glucocorticoids (such as cortisol), androgens (such as testosterone), and estrogens (such as estradiol) occur. The last two are the most important for our situation, as lust is mediated (primarily) by testosterone and estradiol [15].

An important thing to remember is that both men and women produce androgens and estrogens, in fact estrogens cannot be produced without androgens first being created.

What do these hormones do:

Testosterone is the primary male sex hormone, but is used for increasing libido, or one’s sex drive, in both men and women [17]. Testosterone serves many functions in the body, the most significant being primary and secondary sex differentiation in men [18]. For both sexes, it causes body hair growth, muscle growth, bone density increase, and mood (although its specific effect on mood is not well understood).

Testosterone is essential in one’s health, preventing osteoporosis, a condition of irreversible bone deterioration [19].

For lust, the important aspect is that testosterone is what causes you to feel sexual desire for your partner [15].

Estradiol is the primary female sex hormone, and also serves many functions, the most significant being secondary sex differentiation (not primary, interesting*) in women, and for both sexes, it serves important roles in the closing of bone growth plates, bone structure, fat structure, neuroprotective properties, cardiac effects, and once again mood (also not well understood) [20].

Estradiol is also essential in one’s health, reducing the risk of neurodegenerative diseases like Alzheimer’s and Parkinson’s [21], preventing osteopenia [22], a precursor to osteoporosis, and prevention of cardiac ischemia [23], a disease where one’s heart muscles can’t pump hard enough to maintain blood flow.

For lust, the important aspect is that estradiol mediates menstrual and ovulatory cycles, and on average, women have higher sexual desire during ovulation [15].

The final component of love is attachment

Attachment, like attraction, causes sensory inputs to trigger the hypothalamus, where it interacts in the OT-VP pathway, which is a component of the central nervous system, inhibiting oxytocin(OT) reuptake and vasopressin(VP) reuptake [15].

Oxytocin is also a neurotransmitter, like with attraction, but it’s a peptide neurotransmitter (neuropeptide), where dopamine, norepinephrine, and serotonin are monoamine neurotransmitters. Monoamine neurotransmitters generally have a more central role in nervous system function [24].

What do these hormones do:

Oxytocin, often called the “cuddle hormone”[sic] [25], serves important roles in social bonding (especially post birth between mother and child), reproduction, and childbirth. It’s thought that low oxytocin levels may contribute to personality disorders, pair bonding issues, anxiety, and developmental disabilities. Oxytocin is believed to assist in social learning by ways of decreasing noise in the auditory system, increased perception of social cues, and targeted social behavior [26].

For Attachment, oxytocin is what creates human “in-group” behavior [27], which is instrumental in the formation of both platonic and romantic relationships. Oxytocin also provides a pleasure response in both men and women during sexual activity and orgasm [28].

Vasopressin, also known as antidiuretic hormone, primarily serves in nephron (the important part of kidneys) filtration [29], and arterial blood pressure increase [30]. This is a vital function in keeping you alive, without vasopressin, you would quickly die of kidney failure [31].

In the context of attachment, it is not well understood exactly how vasopressin assists with social bonds, but the OT-VP pathway shows that vasopressin is at the very least a complement and assistor to the social roles of oxytocin [15].

TLDR:

For those that want to skip the science, essentially,

• dopamine and norepinephrine cause romantic attraction, and the associated physical effects such as increased sweat and blushing.

• Testosterone and estradiol cause sexual desire

• Oxytocin creates long-term social bonds

Note from the author: Many individuals, such as myself, don’t experience sexual attraction, and similarly many individuals don’t experience romantic attraction. This is not an issue with the individual, but a conclusion drawn from the knowledge that romantic and sexual attraction exist on a bi-modal spectrum, where a statistically significant portion of the population experiences romantic and sexual attraction towards men and/or women. As are many aspects of human biology, humans like to put things in boxes, it’s just a symptom of our pattern recognition skills, however actual biology is incredibly complex, and almost everything exists on a spectrum, no biological processes in humans are identical, even on a cellular level.