Exploring the Heart-Brain Connection and Cannabis Use with Dr. Larry Keen

Exploring the Heart-Brain Connection and Cannabis Use with Dr. Larry Keen

In this episode of Human Science, host John Drummond sits down with Dr. Larry Keen, Associate Professor at Virginia State University. They discuss the fascinating world of psychoneuroimmunology as Larry sheds light on the heart-brain connection and its interplay with substance use. A must-listen for anyone 'keen' on understanding the physiological and psychological impacts of cannabis on the human body.

Sep 29, 2023
Dr. Larry Keen headshotDr. Larry Keen headshot
Dr. Larry Keen headshot
Exploring the Heart-Brain Connection and Cannabis Use with Dr. Larry Keen

Exploring the Heart-Brain Connection and Cannabis Use with Dr. Larry Keen

In this episode of Human Science, host John Drummond sits down with Dr. Larry Keen, Associate Professor at Virginia State University. They discuss the fascinating world of psychoneuroimmunology as Larry sheds light on the heart-brain connection and its interplay with substance use. A must-listen for anyone 'keen' on understanding the physiological and psychological impacts of cannabis on the human body.

Episode Highlights

(02:19) - Larry's Background

(5:35) - Heart-Brain Connection and Substance Use

(10:12) - Heart Rate Variability (HRV) and Wearables

(13:24) - Tips to Improve HRV

(16:51) - Making Healthcare Accessible to Virginia State Community

(19:07) - Cannabis Use and the Heart-Brain Connection: Is Cannabis Bad?

(25:33) - Advice for Future Scientists on "The Game"

(28:47) - Closing Thoughts


Virginia Commonwealth University & Wright Center for Clinical and Translational Research website.


Connect with Larry Keen

For anyone interested in collaborating or exploring the data further, Dr. Keen welcomes open communication. Here is where you can find him and how you can get in touch:

Last medically reviewed on
Nov 15, 2023
All-In-One Research Solution for Real-World Data Capture

Labfront is a global startup specializing in health data analytics. It is currently disrupting academic health research through its Labfront platform, a code-free digital biomarker collection and analytics solution. With the recent explosion of sensors in the scientific community, Labfront is helping health researchers process the overwhelming amount of complex data and transition to the data-rich future.



Larry: The way that you smoke or what you smoke can actually dysregulate how your heart beats. People work, their brains work harder if they're using cannabis. So in certain areas of the frontal lobe and subcortical areas, you see a lot more activation than you would in a healthy control.

And on its face, you're like, oh yeah, that's good. You want more activation, right? Well, not for simple tasks. Not for tasks that shouldn't take that much brain effort. So at every turn that I've seen in nonclinical samples, typically cannabis is bad.

John: Welcome to Human Science, a podcast exploring the human element behind the science that shapes our everyday lives. We're powered by Labfront, the go to tool trusted by researchers looking to automate their studies and transform real world data into health insights.​

I'm your host, John Drummond, and today I'm joined by Dr. Larry Keen, Associate Professor and Director of the Behavioral and Community Health Sciences Program at Virginia State University. We'll discuss the heart brain connection and substance use, exploring the fascinating intersections of psychoneuroimmunology, and we'll unpack one of Larry's core research areas, the health impacts of cannabis use.

Welcome to Human Science, Larry.

Larry: Thank you. Thank You I appreciate all the applause and you know, the thunderous yelling that just happened. That was awesome.

John: You know, Larry, we've just gotten to meet over the few times, but I just have loved the way you kind of talk about analogies and life and, and just kind of finding your own path. And so I'm really excited to share with our audience here on Human Science about your journey and really just the, the life of Larry.

Larry: Awesome. Well, thank you for having me. This will be fun.

John: So Larry, I was thinking maybe we could start today by giving kind of in your own words, the start of your career and your journey into science and, and research and the brain body connection. And really maybe if you can just, a high level overview of, of what really matters to you in this space and why you found yourself actually diving so deep.

Larry's Academic Path

Larry: Interestingly enough, it started very vague, but I've always wanted to know why people did things. As I went to school, I started to become a little bit more curious about why people were making certain decisions, why they were doing certain things, and I became a psychology major, felt natural. I got to the end of my undergraduate career and didn't have a real trajectory of what I wanted to do. I spoke to my first mentor really, in Dr. Phyllis Ford Booker, and she was a neuropsychologist and she said, "Hey, you should look into the brain. You seem to have a knack for it." So I applied to Howard University, got into their PhD program in Neuropsychology, and that's where everything kind of just exploded.

My first, graduate school mentor was Alfonso Campbell loved that guy. He was a bio psychologist, turned neuropsychologist, but everything for him was brain related. He had a study that was looking at the psychoneuroimmunological factors of renal health and disease in black Americans. We had data collected and we had everything from creatine and kidney function to heart rate and different cardiovascular measures to neuropsychological functioning like executive function and all these decision making processes, and it was all in one data set. It was my job to analyze said data, clean said data, and report it every week. Anything I found. So as I learned more, I got to explore this data set that was the human body, both mind and body.

I got a little bit intimate with the cardiovascular system and trying to figure out how we could do, how we could assess things. And I met who would be my other mentor in my graduate career, Jules Harrell at Howard University. He is psychophysiology. He was one of the major players in heart rate variability and all these other types of cardiovascular assessment.

He and Campbell were completely opposite. They were the heart and the brain. I had to, in order to do my dissertation, which was exploring executive functioning and heart rate variability, I had to make them believe that the other part was important for it, right? I had to make them co-exist. I had to make them collaborate. Now, it helped that they're brother-in-laws, so they're nice to each other, but scientifically, they, scientifically, they were completely opposite. They didn't do the same thing, so I had to sit them in a room. Explain the heart rate variability and the all of that system in a way that made sense to the neuropsychological side.

That was the thing that kind of told me, hey, this heart brain connection could be a thing. And at the time of my dissertation, I think it was maybe 10, 15 papers out on it at the time that were really focused on it the way that I was. So it was kind of innovative, it was cool, it was interesting. Had no idea what that data would look like in my dissertation, and I wanted it to be, the better your executive functioning, the better your heart rate variability, right? The better your brain, the better your heart. And what I end up finding out is that it's the opposite.

Heart-Brain Connection and Substance Use

Larry: But the interesting thing about it was it was college students and I talked to them, I knew them, but I didn't do the assessment of their complete lifestyle, including substance use. And I knew. They were smoking, they were drinking, they were doing things that might affect the physiological data that might affect the neuropsychological assessments.

So one of the things that I got lucky with as I graduated and I was looking for a postdoc, was, Dr. Harrell had a connection to a William Latimer who was at, the University of Florida and my postdoc was in, substance use, and sexual risk epidemiology. Adding on this component of substance use and sexual risk because the autonomic nervous system is involved in infectious disease, it's also involved in substance use, which that part was the part that kind of tipped everything. That's where I found out substance use affects the autonomic nervous system in a way that we're still trying to figure out to this day. And that was what, a decade ago.

It was a weird path and it wasn't planned, but I got to the heart brain connection and cannabis use.

John: Wow. Larry, what I heard from that, and I don't mean for this to be an oversimplification, but I love how you started really with, in my mind, the cliche style of your heart. It kind of sounds like an analogy for your own research is you knew how to use your heart without being trained, but now your work and your passion feels like you're trying to get scientists to, to put away the compartmentalization of the brain and the heart, and marry those two together and realize that, you know, hey, there's connection here.

Do you mind if, if we kind of take a step back though, because there was a few things that I, I loved you sharing about for a second. One of those being, thinking about your early days of your career, when you were looking at all that data, how did you know what to be asking? What helped you be able to feel that more, that mind connection when you weren't probably feeling the heart of it all?

Larry: Admittedly genuine curiosity, so. You present me with a data set that has all of these factors. I mean, it was literally over a, you know, I think it was over a thousand variables large, and that's on the low side. And I have to clean the data. I have to know the parameters of not only, The range of the self-reported scores, but now I have to look at the clinical cutoffs for creatinine clearance and all these other things.

For me, that's where I started to see the breadcrumbs. So there were correlations between heart rate variability and interleukin six, which is a cytokine, you know, basically when you, when you get sick and molecules that flow through the blood that basically show that you're sick and they react.

It's kind of like the Marines going to fight a war. They're the first line of defense type of thing, right? I didn't know what the hell they were, but I saw that weird correlation. And I find out there is an entire literature on the autonomic nervous system and immune output and that starts a ball rolling. And all of a sudden it evolves into, into its own thing, and I'm able to ask more refined questions about it, because now it's not just the correlations that I'm basing this off of. It is the scientific literature that allows me to ask more eloquent and actually more scientifically relevant questions.

That is how I started. Now I have that basis, right? So all of those articles that I had to read, and I mean there were hundreds that were on different psycho neural immunological factors, now I'm like, okay, there's a clear connection between the mind and the body. There is something intimate between these two. So no questions off the table.

But these are things that I had no idea about that I wouldn't have even asked if I wasn't exposed to not only the dataset, but the human resources that were in so many different scientific fields.

John: Hearing your, your curiosity through that whole explanation is, is just beautiful to me because, you really are doing science in my mind right there.I wanted to keep focusing for a second here on something that I think has kind of become a buzzword in pop psychology as more people are tracking their own sleep data. You know, workout data via wearables, you know, Whoop and, and Garmin and Apple Watch.

I would love if we could talk a little bit about heart rate variability, because I think people are seeing this data point, this metric on their apps now, but they're not quite sure what it means. do you mind maybe diving in a little bit to kind of maybe some low hanging fruit of like, what is heart rate variability and maybe how does it affect somebody?

What is Heart Rate Variability (HRV)? How Do Wearables Measure It?

Larry: Sure. In short heart rate variability is literally the space in between your heartbeats, you know, so we're averaging or we're applying certain algorithms to get a estimate of the space in between your heartbeat. So the amount of effort that it takes for the heart to beat that's one thing. How often it beats is another, that sympathetic activation, if we remember, the parasympathetic and sympathetic nervous system fight or flight. One is relaxed and, you know, so that you can process food and et cetera. The other is when the bear runs into the room, you gotta be able to get out of there.

Heart rate variability is a indirect assessment of that. It may not be to that scale where that bear is chasing you all the time. If your heart feels like it is being chased by the bear all the time, you might be anxious. You might have some psychological disorder that is constantly leaving you in worry and things like that. Your heart rate variability will be lower typically in those scenarios. The higher your heart rate variability, the more flexible you are. You want it to be variable, so if that bear pops in the room, you're able to go into fight mode. Or flight, depending on what you wanna do.

The interesting thing about it is we haven't necessarily determined clinical cutoffs for it yet. So it's not like if you're between this range and this range are great. For a lot of people, high heart rate variability in general is good.

People using them on wearables is a little bit more advanced, and I say advanced because we use electrocardiograms to actually get the heart signal. Those are clean, the cleanest methods we have. So if we could say the ECG or EKG, depending on what country you're in. That's kind of like your, ethernet cords. You know, you're going to get great service. It's going to be consistent. Everything is going to be efficient that way. Wifi, on the other hand, are like your wearables where yes, it does the exact same thing, but you're relying on something that's a bit more indirect, something that's a bit more crude to get you your information.

The wearables are, yes, they're functional and I'm using them in my research and we're starting to develop a bit more refined algorithms to apply that data. But technically it is not as pure or not as clean as the EKG, but we are moving into a space where it is becoming a lot more acceptable to use it.

Tips to Improve HRV

John: And then if you don't mind thinking about some. Some actionable tips people might be able to to use to improve their heart rate variability.

Larry: Aerobic air exercise and, you know, healthier lifestyles, anything cardiovascular health related in a positive sense will in, can increase heart rate variability. In terms of sleep, ultimately what you want is less disturbances in sleep and higher quality of sleep overall, that typically is associated with better heart rate variability.

John: Yeah, the kind of antidotal situation that I'm finding is, you know, I work often very late into the evenings and my heart rate variability is just like you said, it's like I'm, I'm getting chased by a bear when I'm trying to go sleep in next hour. And my body's like, nah, man, you just, you were just getting chased by a bear a second ago on a work call.

Larry: That's right.

John: There's no way we're sending you to bed now.

Larry: Right. And I mean, think about, you know, for students, like when they're going through exam periods and they're not sleeping and all that stuff, they always have the sniffles, they're always coughing. Their body is fighting to stay awake, but also fighting to keep off the normal pathogens that they could get off if they were resting.

The heart rate variability angle is so cool because it ties to everything. There are frontal lobe structures that can, that have influence on the way that your heart beats. So if we're talking and, you know, central autonomic network and all these other things, things that regulate your body, right? If we're talking about all of that, some of the same structures and pathways are involved in you being anxious, you being worried, you stressing about things, or you having to constantly balance all of these different things. Those are the same pathways that are controlling your heart. Why wouldn't your heart react that way?

If you're overloading your frontal lobe and those structures with all of this other activity, that's the thing that's keeping your heart rate in a parasympathetic mode, so to speak. If you're relaxed, all of that pressure's off the brain, and this is crude, but all that pressure is off so your brain can kind of regulate the body. It can take care of itself. If you're making it work on other stuff, the heart is one of the first things to tell you, hey, this is a problem.

John: Yeah. It's wonderfully explained right there. Thank you so much for that. And you know, if you're listening and you're, you're studying for anything, I think the takeaway from me is, hey, you know, prioritize yourself. Maybe pacing that, studying and not trying to cram.

Larry: Yeah, taking breaks and, you know, time management that they tell you in the first grade and undergrad and grad school and first day on the job. Time management is key. If you know your exams are coming up in a month, start structuring it so that you're not panicking the night before and cramming like I did.

John: So thinking then, if we can kind of zoom back out now, thank you so much for, for, diving in with me there to, to the data some stuff. But zooming back out now big picturing your life cycle of your career. Did you have any compass setting, any directional heading of like, okay, I want to go this way every step of the way?

Making Healthcare Accessible to Virginia State Community

Larry: I never had an end goal, and to be quite honest, I still don't, because it changes. Now, I am an associate professor at Virginia State University. I have NIH funding. Everything is nice and my students are thriving and Virginia State just gave me internal funding to start a center. Now, two years ago was I trying to start a center? No, that wasn't the vision.

Now the center, which the acronym is C OTTER, and it stands for the Center for Outreach and Treatment Through Education and Research. And it has a nice little cute little, sea otter. And it's adorable. We're gonna provide healthcare access to the Virginia State surrounding community. You know, working with the Virginia Department of Health, working with local psychologists, working with other researchers, we're gonna create something that is helpful to the community.

Is that what I pictured as a postdoc? Nah, I was still trying to figure out how cannabis influenced the brain and the heart. Now it's taken me to a place where I can help not just my community, but researchers. Other researchers reach the community, other entities engage with Virginia State and the community. We're providing healthcare access to a place that is not very accessible. They don't really have a lot of access. It's not where I thought I was going.

John: Yeah, it seems that that's been, you know, kind of the thread of this episode is the curiosity. Opportunities came and you were curious and, and you knew how to apply yourself to them. And so first of all, congratulations. I also just love your acronyms. C OTTER, I believe also started the PNIRD Lab at Virginia State University.

But you've touched on something here too and, and something that I think is very important to you, and that's talking about the heart brain connection in relation to substance abuse. Do you mind maybe diving into that a little bit?

Cannabis Use and the Heart-Brain Connection: Is Cannabis Bad?

Larry: The heart brain connection and substance use is interesting. Substance use in general, recreationally, without some type of regimen, all bad news. I started looking at cannabis use specifically in HIV patients, right? It was community-based sample. And what I started to notice is that the people who use cannabis had better immune function. And these are all HIV patients, right? And I was like, oh, that's weird. Maybe cannabis is good for you. Right?

Now, HIV is a predominantly inflammatory disease, meaning your body is constantly fighting those cytokines and et cetera. Those marines that I brought up before, they're constantly flowing now because it's constantly trying to fight the HIV. The interesting thing about it is when I try to explore that same type of topic later on, specifically cannabis use on immune function in other samples, it didn't work that way. It didn't say that you were healthier because you used cannabis. It was a little bit different. And when I stratified, of course, by disease states and all these other things, what I found is if you're healthy, cannabis is bad.

John:  Cannabis right now, and, and THC is becoming widely accepted in the us but your studies are maybe finding something differently.

Larry: I would argue that for me, some of the interesting studies that were surrounding cannabis use, of course the sleep related one, people will discuss up and down. Cannabis helps you sleep. And my research and my colleagues' research I've seen, yes, it does help you fall asleep. That is a thing. It will help you fall asleep. But your disturbances, how long you sleep disturbances meaning not only you're shifting and all that type of stuff, but you waking up, all of those factors go up if you're using cannabis. Now, of course this needs to be replicated in larger, larger samples and things like that, but I've seen it in other studies as well where cannabis helps you fall asleep and they publish it done deal, but they don't look at the rest of the sleep quality components.

Cannabis is associated with, and there's a paper that we're actually writing now, poor eating behaviors. Now it goes to the old adage of, you know, you get high and you go and snack, right? But it's not just snacking, it's overall poor quality of, nutritional intake. Sweets, it's sugary, it's potentially fatty meals and things like that. You're more likely to eat those. And I don't think it's just when you're high, you've now changed your lifestyle to kind of fit what you like to eat, So this nexus of lifestyle choices and your physiology already put you at risk.

Now, compound that with substance use, specifically here, cannabis use, we don't know how those factors are actually gonna come together and jell. For some people, yes, they're fine.They go to work, they come home, they blaze something, and they sit out on a deck and look at the stars, and they're happy. That's their life. There are other people who smoke once end up in the ER, which is, there are, there's clinical studies that have seen people's heart stop, you know, because they smoked once and that sympathetic and parasympathetic dysregulation happens and their heart just can't take it. That's one of the things that's interesting for heart rate variability there.

But you know, that's me getting super nerdy about it. But ultimately, the way that you smoke or what you smoke can actually dysregulate how your heart beats. People work, their brains work harder if they're using cannabis. So in certain areas of the frontal lobe and subcortical areas, you see a lot more activation than you would in a healthy control. And on its face, you're like, oh yeah, that's good. You want more activation, right? Well, not for simple tasks. Not for tasks that shouldn't take that much brain effort. So at every turn that I've seen in nonclinical samples, typically cannabis is bad.

So, is substance use bad on its face? I would argue if you are a healthy, typically functioning and normal adult, you should not use drugs. Drugs are bad. Excuse the South Park reference. If you're gonna use them recreationally, then cool. Learn the rules so that you can actually, if you're gonna do this, do it safely, but I would not recommend.

John: Yeah, yeah. The findings are surprisingly negative in the sense of how it's connecting back to our, our brain heart connection there.

Larry: If I may, I will say this in full transparency. There are studies that have null findings where they don't see any differences between cannabis use and non-cannabis users. There are some people who say yes, some, slight better neurocognitive abilities or performance in cannabis users versus non, but no one will stand up and say, this is better for your cognition. No one will stand up and say, this is better for your heart if you are a normally healthy person.

John: I think that's a great clarification too. Seems like there's, again, connections to overall lifestyle choices. Different preconditions too. You know, stress and trauma and all the ways that, our, our psychology translates to our physiology. Thinking Larry, you know, as we kind of begin to wrap this up, is all these things have been so curious to you as it, as it feels, and thinking of maybe someone listening who's entering the world of, of science, is there any advice you might have for them. You know, mentorship, curiosity, and anything you'd like to share on that note?

Advice for Future Scientists

Larry: Number one, never let anyone tell you you can't do something. This is within reason now, okay? Don't try to take over the world, but if you have a strong scientific curiosity, if they tell you no, you make them tell you why. I think that's important.

I think really having a healthy scientific discussion with your colleagues and your mentorship team and anybody else you can, I think that's necessary. Having a mentorship team is important. If you have one person and you just go to them for advising for your classes, that's not enough.

You need to have a team of people who are interested in your individual development. For me, I got lucky, and I think I've said that a few times, but I genuinely did. You build, you develop, you integrate everything that they pour into you or suggest or talk about, integrate it into your notebook of knowledge and say, how does that tie into what I wanna do or what I'm interested in? For me, it took a while to figure out how to bring those two pieces together.

And realistically, I will argue that I'm kind of in that prime phase now. During my undergrad years, oh, I was a terrible rookie. I came in, I was talented, but I didn't know anything. I was just good at it. I got to my graduate career and I was like, oh, okay. This is how the game actually works. But everybody's better than me. I don't know enough and I can't do what everybody else is doing. And it took kind of my postdoc to put me into a, well, the end of my graduate career and my postdoc to put me in a space where, wait, you can do this.

I'm sitting in a room full of older, predominantly white men, and they're looking at me saying, "Hey, what do you think?" And I was scared ***less. But I did it and eventually I got to the point where I was confident enough to start shooting my own shot, and that's where I started to enter this prime. So like in the past three to four years, I've kind of hit this spot where the game has slowed down for me and I still have the physical quote unquote, talent to pull it off.

For me, the game is starting to slow down and I can see the NIH funding and how to do it and how to navigate it. I can see how to bring my students up with me, so that they get the exposure and that they can start to see how the world actually works. If I was going to say this to my students, junior faculty even, or even some of my peers, what I would say is, whatever your talent is, make sure you have that, but make sure you start to learn the game. So that you can play it properly. It's not just enough to be smart anymore.

John: Mm mm.

Larry: That curiosity has to drive everything, and that exposure has to show you where your curiosity can take you.

Closing Thoughts

John: Coming in as a rookie with the talent and not knowing really how to strategize and how to run plays and schemes, and now the game is slowing down for you. Larry, thank you for, for sharing that. That's, that's a beautiful analogy for, for diving into careers, I think in any field.

Do you mind sharing any place where people can find more about you?

Larry: Sure. I am affiliated with Virginia State University, so of course my profile is there. You can also find me on the PNIRD.com webpage. That's for my lab. All of my papers, all of my colleagues papers who are affiliated with the lab are all listed there. You'll see my students and their research interests. So if you're looking for grad students or you're looking for postdocs, this might be a good place.

If you're looking to collaborate, feel free to reach out to me. My email, lkeen@vsu.edu. If you want it to come and just play with the data, feel free. I'm open to chatting. I set up time to talk to anyone, so shoot me an email, gimme a call, and we can see what we can do.

John: Larry, you are becoming the, the wise coach, the mentor now of the budding mentees. And just, it's beautiful to, to see you now, kind of giving back even more to, to the up and coming and for sharing your time with us. So thank you so much for joining us on the Human Science Podcast.

Larry: Thank you so much for having me and for the most eloquent and polite way I've ever been called old in my entire life. I appreciate it.

John: Now you're seven years in the game, you're about to get that championship ring.

Larry: That's what I'm hoping. This center might be that ring. I mean if we can provide healthcare access, that'll be nuts. We haven't engaged the community in that way and it kind of starts to put Virginia State on a different type of map. But yeah, this is awesome. Thank you. If I can be of any help to anyone, please reach out.

John: Awesome. Thank you so much, Larry. I wish you continued success and thank you for keeping that curiosity alive.

Quotations Icon
Hardvard University Logo Image
“Now, more than ever, we need tools like Labfront that can help researchers take their research and data collection virtual.”
Dr. Gloria Yeh
Dr. Gloria Yeh, MD
Associate Professor of Medicine, Harvard Medical School
Hardvard University Logo Image
Quotations Icon
Bar Ilan University logo image
“The Labfront team was extremely responsive to our requests and made every effort to accommodate our unique needs.”
Yogev Kivity image
Yogev Kivity, Ph.D.
Senior Lecturer of Psychology, Bar Ilan University
Bar Ilan University logo image
Quotations Icon
Oklahoma State University logo
"Labfront's analysts understood our needs as researchers and saved us weeks of work when they prepared our datasets for analysis."
Bryan Edwards headshot
Bryan Edwards, Professor, Joe Synar Chair
Management Department, Oklahoma State University
Oklahoma State University logo
Quotations Icon
Clemson University Logo Image
“The physiological data really helped provide deeper insights.  We recommend Labfront and will definitely be using it again!”
Dr. Kristin Scott image
Dr. Kristin Scott, PhD
Professor of Business, Clemson University
Clemson University Logo Image
arrow icon