Rhonda: You just had a study that I just read, I think, yesterday on sleep and it affecting behavior, loneliness, or...

Matt: Yeah, so we just published a sleep study demonstrating that sleep loss will trigger viral loneliness. And it was a three-part study. I mean, firstly, the reason that I got into this was loneliness is a killer. We know that there is a massive epidemic of loneliness now in industrialized nations. Being lonely increases your mortality risk by about 45%. In other words, being lonely is twice as risky for your death concern than obesity...

Rhonda: Wow.

Matt: ...which is striking.

Rhonda: Yeah. There was actually a study showing loneliness changes, like, a massive amount of gene expression and, like, up-regulates NF-kappaB, cortisol, like all these pro-inflammatory genes. So it makes sense that it'd be associated with...

Matt: And what's bizarre about loneliness...By the way, I'm taking a complete...this has got nothing to do with sleep. But if you look at the profile of your gene expression and your immune system, you've got some immune components that will go after viruses. And viruses can only be transmitted from one human being to another by way of touch. They can't live outside of our bodies. Bacteria, so if you scrape yourself on a fence, like, you know, walking past it, you can get a bacterial infection because bacteria can live outside of the body.

When you become lonely, your gene expression shifts you away from a profile of immunity that normally deals with viruses and pushes you to more towards a bacterial defense profile.

Rhonda: Really?

Matt: Isn't that incredible?

Rhonda: Yeah, you should send me that study.

Matt: That your psychology...

Rhonda: Yeah, that's fascinating.

Matt: And there's a couple of folks at UCLA, who, if you ever have interest in this area of how loneliness, the mind, the mood...

Rhonda: Oh, totally. Yeah.

Matt: Okay, I've got to give you these people. I'm a complete fan of...

Rhonda: Please do.

Matt: ...their work. And they did this study. And it just blew my mind. How could a concept that is so sort of, you know, out there, and some people almost don't, you know, believe in loneliness. Toughen up. What's wrong with you? Go out make some...How could that change the expression of your genes and even alter how you, the organism, fend for yourself from an immunological perspective shifting you from viral to bacterial defense. But, anyway...

Rhonda: Wow.

Matt: So coming back, I was desperately concerned about the state of loneliness. What's interesting, I was reading a lot at the time, because we do a lot of work with sleep and psychiatric disorders including anxiety, and when I was reading the studies where they would take animals and they would deprive them of sleep, you've got this anxiogenic profile where you got cortisol increasing, you got shift in insulin and glucose regulation, all of the bad things that you would not wish to happen, an anxiety increase, they had fear-like behavior all by way of just sleep restriction.

But what was also interesting is that sometimes the researchers would note, despite not measuring it systematically, that the animals, who would often be secluded by themselves in the cage, even when they were with other conspecifics, and other conspecifics would not approach them either.

Rhonda: Okay.

Matt: And so it seemed to me just from reading this, I thought, well, this seems like an animal phenotype of human loneliness. And it seems to be caused by a lack of sleep. So we decided we had to do the study.

So the first part of the study, we took a group of individuals, and they went through the study twice. They were either deprived of sleep for an entire night, or they got a full eight hours of sleep. The first test was, do you have a social repulsion boundary, and that boundary is increased when you are sleep-deprived. So I think everyone has that sense that if I start moving closer to you, you think, okay, do you know what, at some point, that's kind of enough. That's about my close distance.

What's interesting is that if I ask a sleep-deprived an individual to stay put, and I ask you, as an experimenter, to walk towards the sleep-deprived individual, and the individual says, "Stop," when they feel comfortable relative to when that very same individual has had a full eight-hour night of sleep. When you're sleep-deprived, you decide to push people a further distance away from you. So you have a lower desire for social proximity and social interaction.

Second, we then replicated that finding, but now we had them inside the MRI scanner. Because we wanted to see what was changing the brain to produce this social repulsion. What we found was that the regions of the brain that are essentially an alarm network, which is a sort of a stay-away-from-me network that is sort of in the parietal cortex and the premotor cortex, it's sort of what we call the near space network. So it creates your comfort of boundary. And when objects start to approach you, it alarms to say, "Incoming. Be cautious. Be wary." That part of the brain became hyperactive when people were sleep-deprived...

Rhonda: Wow.

Matt: as if you were getting this repulsion signal from the brain. If that wasn't bad enough, the other parts of the brain that have been called the theory-of-mind network, which sort of helps you understand the intent of other people, it's a pro-social network in the brain, it cooperates pro-social interaction, that part of the brain was shut down by sleep deprivation. So it's a double-edged sort of sword.

So we weren't satisfied with that. Next, we wanted to say, "Could someone who just looked at these sleep-deprived individuals, could they actually judge them as being lonelier and looking lonelier and beaten, sort of perceived as lonely, even though they knew nothing about the experiment?"

So in the experiment with the sleep-deprived individuals, we also did videotaped interviews with them. And we just asked them general questions. Tell us about a movie that you watched? Or what was happening in the news this week? Just bland stuff. And then we got 1,000, I think was it was over 1,000 people, 1,083 people online. And they knew nothing about the experiment. They didn't know it's about sleep, sleep deprivation, knew nothing.

And we showed them just a 60-second clip of these people when they'd have a good night of sleep and when they were sleep-deprived. And we just asked them, "How lonely does this person appear to you?" And they knew nothing. But despite knowing nothing, they consistently and reliably rated the sleep-deprived version of the individual as seeming lonelier.

We also asked them, "Would you socially interact with this person? Would you friend them on Facebook? Would you work with them in a business environment?" And they consistently rated that they would prefer not to engage and interact with them.

Rhonda: Is that because they just looked unhappy or looked...?

Matt: Well, we actually think it's a collection of things. It's that their appearance, but also their vocal tone, is very different. We think there's a lot of...This is now one of the key things. What's communicating this asocial profile?

Rhonda: Oh, so they are listening to them speak?

Matt: So they watched them, and they listen to them speak. So they could hear them as well. So we demonstrated that. There was, unfortunately, the social repulsion on both sides of the equation. When you're sleep-deprived, you yourself don't want to have anything to do with other people. And that perhaps wouldn't be so bad if people would only at least come to your rescue, because they would see you in need. The opposite is true. People find you socially repulsive as a consequence. So there's a push from both sides of the social dyad.

The next thing, we asked those people who were rating the sleep-deprived individuals, we also said, "Look, how lonely do you feel after just the 60-second clip?" And they themselves felt lonelier after interacting with sleep-deprived individuals. In other words, this contagion of sleep-deprivation-induced loneliness.

Rhonda: So I wonder how much of this can be translated to, like, someone that, say, for example, gets only five or six hours of sleep versus, of course, not getting a full night sleep. You know, maybe there's, like, a little, just a little bit of this penetrating...

Matt: We then asked that question. That was the final part of the study, which is that we said, "Okay, this is extreme sleep deprivation, and most of the population does not undergo this. What about a more ecological version?" So we tracked hundreds of people across two nights of sleep. And we asked, just by a subtle variation of nature, our small perturbations of sleep from one night to the next, do they predict how lonely you experience yourself to be from one day to the next? And these are small minute changes in sleep efficiency, just small reductions in sleep of tens of minutes.

Lo and behold, even just that small change in your sleep from one night to the next, we could measure, predicted how lonely you would experience life the next day from one day to the next. So it doesn't even take, you know, two hours of sleep reduction.

Rhonda: Wow.

Matt: Small minutes.