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The chemistry of love, according to a William & Mary professor

William & Mary professor Randy Coleman says hormones and neurotransmitters like dopamine, oxytocin and serotonin impact romantic relationships. (Photo via Shutterstock)
William & Mary professor Randy Coleman says hormones and neurotransmitters like dopamine, oxytocin and serotonin impact romantic relationships. (Photo via Shutterstock)


The chemistry of love, according to a William & Mary professor

Randy Coleman, a chemistry professor at William & Mary, has taught a course on the science of love for 20 years.

This will be Coleman’s last year teaching “The Chemistry of Emotion & Behavior” before retiring after 54 years in the classroom.

He spoke to WHRO’s Doug Boynton about the basic chemistry of one of human’s most powerful emotions: Love.

This interview has been edited for length and clarity.

Doug Boynton: What happens as we become infatuated and kind of feel like we are fallen for someone?

Randy Coleman: The first things that happen most likely are there are regions of the brain that start releasing a chemical called dopamine, which is a chemical that produces a very pleasurable, even addictive effect. In fact, it is the chemical that has led to the opioid crisis, for example. So we know it can be very addictive, but it also is considered to be the love hormone, if you want to think about it like that. 

And as we start falling in love with someone … when we are in their presence, our brains are being flooded with dopamine. That gives us a very nice, pleasurable feeling toward the individual that we're falling for. So it's focused on dopamine initially. Very important, pleasurable type of hormone, addictive type hormone, if you wanted to think about it like that.

D.B: As a relationship progresses, that kind of immediate high goes away. And what is that replaced with? If we figure that the relationship continues.

R.C: If the relationship is continuing, then another chemical called oxytocin can come into play. 

And this is a chemical that helps to produce pair bonding. In fact, when we study various other animals on the planet, in particular the prairie voles, voles are very well known for having high levels of oxytocin in their bloodstreams and they mate for life. So there's a very tight pair bond there. 

So I would say, after you get over the infatuation period, the next important chemical that steps into play is oxytocin. That really triggers the pair-bonding activity between the two individuals who are falling for one another.

D.B: If the relationship goes on the rocks and there's a breakup, people sometimes feel like their heart might be breaking and it's not really their heart. You tell me it's in their brain.

R.C: Yes, it's really in their brain. And if they're breaking up, that can produce a lot of stress in both individuals potentially. 

If we look at the stress hormones then we're starting to get into, things like cortisol and so on, that are being produced by the adrenal glands, which are outside the brain. But those stress hormones through the bloodstream get back into the brain and start changing some of the pathways that were important in the relationship. 

So those stress hormones can come into play at that point, and they can really kind of mess up a lot of the neural networks that are in the brain. It's not good to be stressed out.

D.B: And yet we sometimes will often, hopefully, reach a point where all of that levels out and we go back to what can pass for normal, right?

R.C: Yes. But if you're in a long term relationship, for example, my wife and I are in our 58th year of marriage, so we've gone past the infatuation period, and we're just in a nice, very comfortable, lifelong relationship. We're happy with each other. 

And if I think about happiness, there is another neurotransmitter that really comes into play and that's serotonin. Serotonin is considered to be the happy, contentment type of hormone that gets kicked out in the brain. 

Interestingly enough, most of the serotonin is produced in our gut. So the kind of food we eat can set the mood for our behavior. The serotonin that's produced in the gut, in the microbiome of our gut, the collection of bacteria and other microorganisms in our gut, they're responsible for making most of the serotonin that our body uses. Eventually that gets back into the brain and gives us this feeling of contentment and happiness. 

So I'd say, as the relationship deepens and you get over the infatuation period from the dopamine that's being kicked in, the pleasurable hormone, you're going to settle down and see more serotonin showing up in the brain when you're around your love partner … . And that's going to lead to potentially lifelong contentment. At that point, we're really dealing with two major chemicals in the brain, the oxytocin, which continues to foster the bonding between the two individuals and the serotonin, which continues to produce happy feelings in the presence of the other individual.

D.B: The chemical part of it sometimes doesn't sound very romantic.

R.C: Well, that's the problem, you know? As a scientist, I want to know what's going on.

When the students and I get to talking in our discussions in that course, they sometimes say exactly what you said: You're taking all the romance out of the relationship when you're looking at the nuts and bolts behind the scene. We've opened a curtain, and suddenly we see all these chemicals in our brain that are causing these behaviors. 

And that's fine. I mean, that's the way it is. But we don't have to dwell on it. As a scientist, I recognize what's going on, but Isure enjoy the pleasure of my wife's company and my grandchildren and children and so on. So I don't think about the nuts and bolts leading to that behavior. I just enjoy the behavior which would be enjoying the romantic relationship that you have with your partner.

Doug Boynton is the afternoon host for the “All Things Considered” weekday afternoons on WHRV. He grew up in Michigan, but he believes spending more than half his adult life in Virginia makes him a Virginian.

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