I and many listeners of this podcast are obsessed with dopamine and what is dopamine? How does it work? We all hear that dopamine is this molecule associated with pleasure. I think the term dopamine hits, like I'm getting a dopamine hit from this, from Instagram or from likes or from praise or from whatever is now commonly heard.

What is dopamine and what are maybe some things about dopamine that most people don't know and probably that I don't know either? So dopamine is a neurotransmitter and neurotransmitters are those molecules that bridge the gap between two neurons. So they essentially allow one neuron, the presynaptic neuron to communicate with the postsynaptic neuron.

Dopamine is intimately associated with the experience of reward, but also with movement, which I think is really interesting because movement and reward are linked, right? If you think about, you know, early humans, you had to move in order to go seek out the water or the meat or whatever it was.

And even in the most primitive organisms, dopamine is released when food is sensed in the environment. For example, C. elegans, a very primitive worm. So dopamine is this really powerful, important molecule in the brain that helps us experience pleasure. It's not the only neurotransmitter involved in pleasure, but it's a really, really important one.

And if you want to think about something that most people don't know about dopamine, which I think is really interesting is that we are always releasing dopamine at a kind of tonic baseline rate. And it's really the deviation from that baseline rather than like hits of dopamine in a vacuum that make a difference.

So when we experience pleasure, our dopamine release goes above baseline. And likewise, dopamine can go below that tonic baseline. And then we experience a kind of pain. Interesting. So is it fair to say that one's baseline levels of dopamine, how frequently we are releasing dopamine in the absence of some, I don't know, drug or food or experience just sitting, being, is that associated with how happy somebody is, their kind of baseline of happiness or level of depression?

There is evidence that shows that people who are depressed may indeed have lower tonic levels of dopamine. So that's a really reasonable thought. And there's some evidence to suggest that that may be true. The other thing that we know, and this is, you know, really kind of what, what the book is about, is that if we expose ourselves chronically to substances or behaviors that repeatedly release large amounts of dopamine in our brain's reward pathway, that we can change our tonic baseline and actually lower it over time as our brain tries to compensate for all of that dopamine, which is more really than we were designed to, to experience.

Interesting. And is it would, is it, um, the case that our baseline levels of dopamine are set by our genetics, by our heredity? Well, I think, you know, if you think about sort of, you know, the early stages of development in infancy, certainly that is true. You're kind of, you know, born with probably whatever is your baseline level, but obviously your experiences can have a huge impact on where your, your dopamine level ultimately settles out.

So, um, if somebody's disposition is one of, um, constant excitement and anticipation or easily excited, these are, I think about the kind of people where you say, "Hey, do you want to check out this new place for tacos?" and they're like, "Yeah, that'd be great." And other people are, um, a little more cynical, harder to budge, like my bulldog Costello, um, very, very stable, low levels of dopamine with big inflections in his case.

Um, is that, do you think that's a set in terms of, um, our parents and obviously nature and nurture interact, but is that, is dopamine at the core of our temperament? I don't really think we know the answer to that, but I will say that people are definitely born with different temperaments and those temperaments do affect their ability to experience joy.

Um, and, and, you know, we've known that for a long time and we described that in many different ways. One of the ways that we describe that in the modern era is to use psychiatric nomenclature, like this person has a dysthymic temperament, or, you know, this person has chronic major depressive disorder.

Um, in terms of looking specifically at who's vulnerable to addiction, um, that's an interesting sort of mixed bag because when you look at, uh, the research on risk factors for addiction, so what kind of temperament, uh, of a person makes them more vulnerable to addiction, you see, um, some interesting findings.

First, you see that people who are more impulsive are more vulnerable to addiction. So what is impulsivity? That means having difficulty, um, putting space between the thought or desire to do something and actually doing it. And people who have difficulty putting a space there who are, who have a thought to do something and just do it impulsively are people who are more vulnerable to addiction.

Interesting. Could I, uh, in terms of impulsivity, is this something that relates literally to, um, the startle reflex? Like I, for instance, as a, uh, lab director, I'm familiar with walking around my lab. And, um, when I decide deciding I'm going to talk to my people, of course, when they knock on my door, it's always like, wait, why am I being bothered right now?

Even though I love to talk to them, but I walk around my lab from time to time and some people I notice I'll say, um, do you have a moment? And they'll slowly turn around and say, yeah, or no, in some cases. Um, and other people will jump the moment I say their name, they actually have a, uh, a kind of a heightened, um, startle reflex.

Right. Is that related to impulsivity or is what you're referring to, um, an attempt to, uh, withhold behavior that's very deliberate under very deliberate conditions? Yeah. So I don't think that that startle reflex is, is necessarily related to impulsivity. That, that can be related to anxiety. So people who are high anxiety, people will tend to have more of a startle reflex.

Impulsivity is a little bit different. And by the way, impulsivity is not always bad, right? Um, impulsivity is, is that thing where there's not a lot of self editing or worrying about future consequences. You know, you have the idea to do something and you do it. And of course we can imagine many scenarios where that's absolutely wonderful.

Um, you know, there can be a sort of, uh, let's say intimate, um, interactions between people where you wouldn't really want to be super inhibited about it. Right. You would want to be disinhibited and, and impulsive. Um, there, I can also like imagine like sort of, um, fight or flight scenarios, like battle scenarios, right.

Where, where it would really be good to be impulsive and just go, rah, you know, just where hesitation can cost you your life. Yes, that's right. That's right. But you know, and I think this brings up a really, something that I've come to believe after 25 years of practicing psychiatry is that what we now conceptualize in our current ecosystem as mental illness are actually traits that in another ecosystem might be very advantageous.

They're just not advantageous right now because of the world that we live in. And, and I think, you know, impulsivity is potentially one of those, right. Cause we live in this world that's sort of like, you have to, um, constantly be thinking sort of rationally about the consequences of X, Y, or Z.

And it's such a sensory rich environment, right. That we're being bombarded with all of these opportunities, these sensory opportunities, and we have to constantly check ourselves. And so, so, so impulsivity is something that right now, um, can be a difficult trait, but isn't in and of itself a bad thing.

I see. Yeah. Yeah. And it's, I, I'm beginning to realize it's a fine line between spontaneity and impulsivity. Yeah.