Anatomy of an Affair: The Chemistry of Love


How and why do we fall in love? While love is most often described in magical terms, the emotion of love is created and sustained through biochemical processes in the body – most notably the brain. These biochemical processes are often called The Chemistry of Love.

Different chemicals are involved in falling in love, and the way they relate to affairs are many. The Chemistry of Love can be a very good thing when two people are hunting for a mate..and devastating when allowed to promote an affair. For some, the falling in love causes the affair; for others, a strong sexual attraction or urge is the culprit. For many, falling in love and a strong sexual attraction can be very different emotions.

The Biochemicals of Love

Falling in love and strong sexual attraction can be different emotions, and they can exist separately because each involves separate biochemicals.

The Chemistry of Love: Sexual Attraction

The sexual attraction part of the Chemistry of Love is driven by the chemical testosterone. This is true for both men and women. It is the chemical responsible for sexual response, an urge to mate and is the driving force that peaks during the plateau phase of sexual arousal.

The Chemistry of Love: Romantic Love

Some of the other chemicals that are involved in the Chemistry of Love include phenylethylamine (PEA), dopamine, oxytocin, norepinephrine, serotonin and adrenaline. All of these work in the brain and other organs of the body to produce certain feelings or changes in body function. Recent studies indicate that vasopressin might be involved in the process as well.

PEA – Phenylethylamine

The start of an affair – or any romantic relationship – often begins with PEA. This chemical is responsible for creating connections between nerve cells in the brain among other things. It also is responsible for stimulating the release of adrenaline from the pituitary and results in shortness or quickness of breath, increased heart rate and other physiological responses. A very mild version of PEA is found in chocolate, which explains why so many people really like chocolate.


The next chemical is dopamine. This is the neurotransmitter that when released in the pleasure center of the brain causes feelings of euphoria, intense pleasure and is actually responsible for the addictive nature of such things as cocaine or alcohol. In the early falling in love or what is called the infatuation phase of a relationship, dopamine is the cause of the strong feelings of wanting to be together increasingly often and for longer durations.

Since dopamine produces a strong sense of pleasure, in what is called the reward center of the brain, it is this reward that causes an addict to pursue ever more of the addictive substance. In the case of infatuation, this is what drives the lovers ever forward to get more of the pleasure each brings to the other in the relationship.

Increased levels of dopamine also cause a decline in serotonin in areas of the brain related to a sense of well-being or stability of thoughts. Low levels of serotonin lead to depression, but also to other reactions as time goes on. Studies using functional magnetic imagining to measure areas of the brain that light up or react to reduced levels of the chemical found them to be the same areas involved in Obsessive Compulsive Disorder. This may be the cause of the lovers obsessing over one another and all the other symptoms of this disorder that manifest themselves during the infatuation phase of a relationship.

Alcohol stimulates dopamine and so also has an effect on serotonin levels and might be one of the reasons so many affairs are related to alcohol consumption. Other drugs like cocaine, heroine, and even some prescription drugs can produce similar effects at times.

Note: Effexor is reputed to have this effect. Effexor also can depress the judgment center of the brain, which lowers inhibition levels. 


Oxytocin is an amazing substance. It is the chemical that seems to be the cause of a bond between two individuals. It also appears to be the chemical responsible for the rewiring of the brain as we develop our memories. Only three percent of animals have high numbers of receptors for oxytocin in certain areas of their brains, and those that do have them tend to either be species that mate for life or the type where mother and father of offspring remain committed and together until the offspring are able to fend entirely for themselves.

Recent research on two types of voles has shown that the prairie vole which has high oxytocin levels will remain mated to one another for their entire lives, even raising multiple litters of young, and staying together even after they are no longer able to reproduce. These fury little creatures related to mice also seem to avoid other members of the opposite sex that are not their mate.

By contrast, their cousins, the Mountain or Montane voles are indiscriminate maters and move from one night stand to one night stand. They have very few receptors for oxytocin in key areas of their brains and much lower levels of the chemical.

In humans, the highest levels of the chemical are present in women just before they give birth. Interestingly, it appears that higher than normal levels of the chemical also exist in men who are present for the birth of their children and those levels remain higher than typical for some time after the children are born.

The next highest levels of oxytocin in both men and women seems to be immediately following the climax phase of the sexual act. In men, vasopressin also seems to be higher immediately following sex, and some have called the chemical the connection chemical.


Norepinephrine is related to amphetamines and can cause suppression of appetite, a rise in blood pressure and manic episodes similar to prolonged amphetamine use. It also can play a role in an affair, as well as a role in that feeling of being in love so many of us recall from when we were dating our spouse. It can cause us to feel happy – even giddy – and who among us has experienced that feeling when but teenagers as we fell in love for the first time?

The Chemistry of Love Is Similar to Addiction

Yes, I said addiction. Romantic love shares many characteristics with addiction due to the chemistry of love, as I will explain.

The Brain’s Reward System

As it relates to affairs, the reward system deep in our brains neither processes nor analyzes rational decisions and does not think in logical ways. It simply reacts to various kinds of stimulus, and this is at the heart of our emotional response to others. During the infatuation of an affair, higher than typical levels of dopamine cause addictive reactions similar to those of a crack addict getting high. At the same time, the high levels of dopamine appear to reduce the levels of serotonin, which can cause substantial behavioral changes such as depression, mood swings, obsession with the source of the addiction (that would be the affair partner) and other psychological manifestations.

The Biochemistry of Addiction

The way addictive substances work in the brain varies; however, the result of those various chemicals or substances as they relate to brain chemistry is really much more subtle.

For example, opiates affect the dopamine reward system differently than does a depressant such as alcohol. Heroine and other opiates (such as morphine) decrease the activity of gamma-aminobutyric acid (GABA). GABA moderates the effects of dopamine by causing the receptors that accept dopamine to release the substance so that it can be reabsorbed into the neuron that sent it across the gap to stimulate the dopamine receptors in the first place. Heroine masquerades as GABA and replaces it in the receptors designed to latch onto it thereby preventing GABA from doing it’s work. The result is a sudden rush of euphoria and feeling of warmth that seems to permeate the senses.

So while heroine does not increase dopamine levels directly, by preventing a brain cell from releasing the substance it allows the effects to accumulate and the cell itself reacts as if extremely high levels of dopamine were present. Opiates do this simply by blocking GAB from being able to attach to the neuron thereby allowing dopamine to accumulate on the cell instead of being recycled.

Nicotine acts this way as well, though the overall effect is much more subtle. The process is very similar to  heroine’s, since it ties to the same receptors and prevents GABA from doing its job to reduce the build up of dopamine on an individual cell.

Other chemicals that are addictive modify the chain of events in differing ways; however, what I am talking about here is how the brain is affected by the reward system involved in falling in love or having an affair. Given that, I don’t see how the mechanism of how the results are achieved greatly matters, since the net effect is the same for the feeling of falling in love as it is for becoming addicted to heroine. The degree to which a substance is addictive is more closely related to how radically it modifies brain function than to the way it works on the reward system in the brain.

True addictions also display an increased resistance to the substance over time and ever more of the substance is required to achieve the same net effect. PEA levels easily triggered in early falling in love stage of a relationship drop over time, and more stimulus is required to maintain the same feelings and sense of reward as time progresses. As PEA and the indicated dopamine levels drop, more and more stimulus is required to return to the previous states of euphoria, well being and obsession with the object of our love. This indicates to me that the mechanism is really pretty much the same as for a hard addiction  – such as even heroine or crack.

Some addictive substances also affect other parts of the brain, as well, and can even affect other organs. Many of these are not related to the addiction as it relates to the psychological effects of the drug or substance but can be quite pronounced. Most of these effects are related to continued use of the drug and can cause detrimental effects in the heart, lungs, kidneys, liver and other vital organs. However, the way the brain perceives them is remarkably similar. and while falling in love does not typically cause long term effects in the liver like alcohol does, the reward system is at the heart of the addictive properties of each.

Another indication of true addiction is symptoms of withdrawal which can vary in intensity from substance to substance. These can include depression, loss of appetite, sleep disruptions, anxiety, phobias and even delusions. Again, I think that falling in love meets the same criteria., because withdrawal from a lover can have many of the same symptoms as withdrawal from an addictive substance.

Recovering From Addiction

I also think that many of the same steps for recovery from a chemical addiction apply to recovery from an affair as well. This similarity is especially true of depressant addictions which can be impossible or at least very difficult to overcome unless complete deprivation of the source of the addiction is maintained. Any drinking by an alcoholic feeds the addiction and anyone who has truly been addicted to alcohol would be advised to avoid all drinking if they hope to maintain sobriety. Likewise, in an effort to minimize the possibility of a rekindling of an affair it is in the best interest of one time lovers to avoid any contact with each other if they hope to stay clear of the effects of interacting with each other going forward.

There is a recent tool that has become available for researchers looking into the way certain things affect our brains. One of the very newest is functional Magnetic Resonance Imaging or fMRI. While MRI technology has been around for a while, fMRI allows looking at real time function of various internal workings of the body. This includes the brain which can be studied as certain types of events take place and not just the long term effects or echoes of things that happened as in the recent past. In one study something as simple as being presented with a photograph of a lover indicated a spike in activity in areas of the brain related to the dopamine reward cycle. Similar studies are still ongoing as to what areas of the brain are effected by certain types of substances and other stimulus of various types, but the same ares, those related to the dopamine reward system are highly, even hyper-active in both heroine addiction and feelings of being in love.

So some might argue that a feeling can’t be addictive in the same way as a substance such as crack or morphine, the parts of the brain are effected in quite similar ways and since the dopamine reward cycle is at the heart of the way we learn to equate the reward to the stimulus and seek out its effects in an obsessive manner, I think the current bulk of research would indicate a direct correlation between falling in love and becoming addicted.

Still to be studied very much are inhalants which are pretty hard to do trials on since many of these have toxic and severe effects on multiple parts of the body. Testing them would cause serious harm to the subjects under testing in most cases and so many of these are left to the theoretical realm along with various psychoactive drugs like LSD which can cause long term psychosis and other hazards too dangerous for much continued research.

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16 Responses to Anatomy of an Affair: The Chemistry of Love

  1. Pingback: Is an emotional affair an addictionSurvive Your Partner's Affair

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  4. Markus says:


    Great work, but I’d like to see some references at the end of the article too.

    You don’t want to be putting something this well written out there without legitimate references at the end of the article.

    • Mark1952 says:


      This was derived from a series of posts on our discussion forum. Some of the embedded links point to references of sorts but because of the way the original discussion took place there never was what might be considered a bibliography or list of references. To go back and assemble that kind of list now would take longer than the original discussion lasted.

      That said, you have given me incentive to try to provide a more complete list of references for future articles and posts.


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  9. Al says:

    I would recommend rewording the term “lover” with infidelity partner, or interloper or some such. Referring to someone’s affair partner as a “lover” really is a tad offensive to the betrayed spouse.

    The last thing I would refer to an affair partner as is a loving person. They are sexually exploitative for the most part. Lover is so far off the mark it’s just inappropriate.

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  12. ken says:

    great, i thought my cheating wife was just a [edited]

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  14. Rodion says:

    Thanks for this article. I’ve heard this talked about before, and read a couple of articles, but this summarizes it pretty nicely. Will pass this along to other interested parties. (There are many out there!)

  15. heidi says:

    Really great article! Explains it all very well

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