Matt: And we've seen this, too, that if you look at that emotional brain reaction signature that I just sort of described, and you repeat that, but with people who are high-anxious and low-anxious, and we know some of the genes that are associated with being high-anxious and low-anxious. So we're using anxiety as a sort of a proxy for perhaps a particular genotype here. What you see is that it's those high-anxious people who are the most vulnerable to this impact of a lack of sleep. Those who are low-anxious still have a bad outcome, but it's nowhere near as bad. So there seems to be sort of interactions here between sleep loss and your basic trait levels of being sort of a nervous, anxious type to begin with.

Rhonda: That makes sense.

Matt: And those are the people who are, sadly, the people who typically don't get a good night of sleep anyway.

Rhonda: Right. So you're saying anxiety is, like, one of the things that stops me from sleeping.

Matt: It's the principal trigger of insomnia.

Rhonda: Yeah, really, true.

Matt: It's the model of insomnia right now, is that you get...And if you look at the nervous system, that's how we understand insomnia right now, is that its principle is...I think ultimately we'll find that there are multiple flavors of insomnia, different forms. We already categorized two of them. We've got what we call sleep onset insomnia and sleep maintenance insomnia, difficulty falling asleep, difficulty staying asleep. They're not mutually exclusive. You can have both, or you can just have one or the other.

But coming back to it, I think the overarching biological red thread narrative of insomnia is an amplified fight-or-flight nervous system, that your nervous system is split into these two branches, what we call sort of the sympathetic and parasympathetic parts of your autonomic nervous system. The sympathetic is anything but sympathetic. It's poorly named. It's the fight-or-flight branch of your nervous system. It ramps you up, charges you up, releases cortisol, adrenaline.

You constantly see an overactive, sympathetic nervous system in people with insomnia. And when you measure their cortisol across the 24-hour period, in most of us, just as we're getting to our natural bedtime, cortisol just starts to now drop down. We start to see that cycling down of cortisol. The opposite happens in people with insomnia. You get a continued rise right around that bedroom period. And it seems to be very predictive of sleep onset problems.

If you look throughout the night, cortisol then starts to plummet, and it drops beautifully down. It's part of the reason why deep sleep is the best form of natural blood pressure medication that you could ever wish for. Your heart rate drops down, your vessels relax, cortisol drops down. But in other insomnia patients, we see this bizarre spike in cortisol in the middle of the night. And it predicts nighttime awakenings. It predicts sleep maintenance insomnia.

Rhonda: I have experienced...So that's one of the problems that I actually have. It's much, much better now that my stress level is, like, maintained. At graduate school, I would get nighttime awakenings where my heart would start racing. And I would wake up thinking that there was a spider or some kind of threat. And I would scream, and sometimes fly out the bed. I mean, you know, and just...it would scare my husband, you know. At the time, we weren't married. But, I mean, you know, these nighttime awakenings, it was something that's dated back for quite some time. But really, it manifested during a very stressful period, and that was graduate school.

Matt: We see that...

Rhonda: Got much better.

Matt: ...so frequently.

Rhonda: Yeah.

Matt: But if you can think about that as sort of, you know, a stress management component to insomnia, you know, it's part of what we call cognitive behavioral therapy for insomnia, which is sort of dealing with that stress, you know, meditation. There's great apps out there, like Headspace, for example.

And the data on meditation and insomnia is very very powerful. You know, I'd known about it a little bit, but I hadn't read really all of the studies until I started researching it for the book. And I was so convinced that I started meditating. And I haven't stopped since. Because it was, you know...Typically, I'm not a bad sleeper. I'm a light sleeper. I'm a pretty good sleeper. I found it hugely useful for times when I was under stress, or when I was traveling and jetlagged. It's very beneficial, too.

But that underlying theme, I think, as a message for insomnia, it's not the only cause of insomnia, but it seems to be if there's one common sort of rule that binds many of the patients with insomnia together, it's this overactive fight-or-flight branch of the nervous system. And if you can settle that down, you are certainly on the path towards better sleep.

Rhonda: Right.