Mark: Here’s a wild thought: over the last decade, public health's number one enemy might not have been smoking or a bad diet. It might have been a single, simple belief. A belief that likely killed more people than homicide. And it’s a belief you probably hold right now. Michelle: Whoa, okay, that’s a heavy way to start. You’re saying a thought is more dangerous than a heart attack? That sounds like something from a sci-fi movie. What on earth is this deadly belief? Mark: That deadly belief, Michelle, is the central demon that Kelly McGonigal sets out to slay in her book, The Upside of Stress: Why Stress Is Good for You, and How to Get Good at It. The belief is simply this: that stress is, in and of itself, harmful to your health. Michelle: Right, and McGonigal isn't just a pop-psych guru. She's a health psychologist and lecturer at Stanford. What's fascinating is that she started her career teaching the dangers of stress, but then she encountered research that completely flipped her own perspective. Mark: Exactly. She basically had to go on an apology tour for her old advice. This book is the result of that 180-degree turn, and it all starts with one landmark study that is absolutely mind-blowing. Michelle: Okay, you can't leave us hanging. What was this study? Because everything I've ever heard, from doctors to my own mother, is that stress will kill you.

Mark: Well, get ready for your brain to be broken. In 1998, researchers in the U.S. surveyed 30,000 adults. They asked them two simple questions. First, "How much stress have you experienced in the last year?" And second, "Do you believe that stress is harmful for your health?" Michelle: Pretty straightforward. I can guess where this is going. The people with high stress died sooner. Mark: That's what everyone thought. The researchers then spent the next eight years tracking public death records to see who from that group had passed away. And what they found was stunning. Yes, people who reported high levels of stress had a 43% increased risk of dying. But—and this is the part that changes everything—that was only true for the people who also believed that stress was harmful. Michelle: Hold on. Let me get this straight. People who had high stress but didn't view it as a bad thing weren't more likely to die? Mark: They were even less likely to die than people who reported very little stress. The people with the lowest risk of death in the entire study were those who experienced a lot of stress but didn't see it as harmful. The researchers crunched the numbers and estimated that over those eight years, 182,000 Americans may have died prematurely, not from stress, but from the belief that stress was bad for them. Michelle: That is… completely insane. It’s like a biological placebo effect, but in reverse. A nocebo. So the danger wasn't the stress itself, it was the narrative we tell ourselves about the stress. Mark: Precisely. It’s the story. McGonigal argues that the constant public health message—"stress is toxic, avoid it at all costs"—has inadvertently created the very harm it was trying to prevent. She points to other examples, like how graphic, fear-inducing warnings on cigarette packs can actually make some smokers crave a cigarette more, because smoking is their coping mechanism for the fear the image just induced. Michelle: That makes a twisted kind of sense. You scare someone, and they reach for their comfort, which is the very thing you're trying to get them to quit. But this stress idea feels bigger. It’s not just about one habit. It’s about our entire physiological response to life. Mark: It is. And other studies back this up. One from Yale followed adults for twenty years and found that people with a positive view of aging lived, on average, 7.6 years longer than those with a negative view. Another found that people who are more trusting of others live longer than cynics. Our beliefs, our mindsets, are constantly shaping our physical reality. Michelle: Okay, but I have to push back here, Mark. This is where some critics have raised a flag. It can start to sound a bit like 'toxic positivity.' For someone dealing with the chronic stress of poverty, or systemic racism, or a serious illness, isn't it a bit dismissive to say, 'Just change your mindset'? The stressor is very real and damaging. Mark: That's the perfect question, because it's not just about 'thinking positive.' It's about changing your biology. McGonigal is very clear on this. The point isn't to pretend the stressor doesn't exist. The point is to understand that your body has different ways of responding to it, and your mindset is the switch that determines which response you get. This moves us from just a philosophical idea to hard science. Michelle: A biological switch? Okay, now I'm intrigued. How does a belief physically change what happens in your body?

Mark: This is where it gets really cool. McGonigal introduces us to two primary types of stress response. We all know about 'fight-or-flight,' which is what she calls the 'Threat Response.' That's when your body thinks it's in mortal danger. Your heart pounds, cortisol floods your system, your blood vessels constrict to prevent you from bleeding out if a lion bites you. It's great for surviving an attack, but terrible for giving a presentation at work. Michelle: Right, because your brain basically goes offline, and all you can think about is escape. I know that feeling well. What’s the other one? Mark: The other one is the 'Challenge Response.' This is what your body does when it sees a situation as difficult, but manageable. Your heart still pounds, but it's a more efficient cardiac profile. Your blood vessels stay relaxed, sending more oxygen to your brain and muscles. You get a surge of energy and focus, but without the paralyzing fear. It’s the biology of courage, of rising to an occasion. Michelle: And you're saying our mindset is what chooses between the lion-attack response and the big-game-performance response? Mark: Exactly. And there's a fantastic study that makes this crystal clear. It's known as the 'Shake Tasting Study.' Researchers at Yale, led by Alia Crum, who did a lot of this pioneering work, invited participants in for a taste test. On one visit, they were given a milkshake with a label that screamed 'Indulgence.' It said 620 calories, 30 grams of fat—a decadent treat. Michelle: My kind of milkshake. Mark: On another visit, the same participants were given the exact same 380-calorie milkshake, but this time the label was for a 'Sensi-Shake.' It said 140 calories, zero fat, all guilt-free sensibility. Michelle: Ah, the sad, watery milkshake of virtue. I know it well. Mark: But it was the same shake! Here's the kicker: they measured the participants' levels of ghrelin, the 'hunger hormone.' When ghrelin is high, you feel hungry. When it drops, you feel full and satisfied. When people drank the 'Indulgence' shake, their ghrelin levels plummeted three times more sharply than when they drank the 'Sensi-Shake.' Michelle: You have got to be kidding me. Their bodies physically registered more satisfaction from the exact same food, just because of the label? The belief about what they were consuming changed their hormonal response. Mark: It changed how their gut processed the calories. The effect you expect is the effect you get. Your body said, "Oh, this is a rich, satisfying treat," and it produced a rich, satisfying hormonal response. When it thought it was getting a diet drink, it produced a diet response, leaving them feeling less full. Michelle: Okay, so this is the science behind why a 'cheat meal' feels so much more satisfying than a 'healthy treat,' even if the calories are the same! It's not just in our heads; it's in our hormones. How does this apply back to the threat versus challenge response? Mark: It's the same principle. McGonigal describes another study where they brought people into a lab and told them they had to give a stressful, impromptu speech in front of harsh, critical evaluators. Classic anxiety-inducing scenario. Michelle: My personal nightmare. Mark: Before the speech, they showed one group a short video explaining that the signs of stress—the racing heart, the sweaty palms—were the body's way of preparing you for a challenge, giving you the energy to perform well. They primed them with a 'stress-is-enhancing' mindset. The other group saw a video about how debilitating stress is. Michelle: And what happened? Mark: The group that was told stress was helpful didn't just report feeling more confident. Their bodies showed it. They produced more of a hormone called DHEA. DHEA is a neurosteroid that helps the brain grow and learn from experience. It's a marker of resilience. The ratio of DHEA to the stress hormone cortisol is sometimes called the 'growth index.' A higher ratio means you're in a state of learning and thriving under pressure. Michelle: So they literally produced more of the resilience hormone just by changing their interpretation of a racing heart. They turned a threat into a challenge. Mark: They turned it into a challenge. And this is the core of the book's 'how-to.' When you feel the physical sensations of stress, you have a choice. You can think, "Oh no, I'm losing control, this is a disaster." That's a threat response. Or you can say, "Okay, my body is getting ready. This is energy I can use. This means I care." That's a challenge response. Michelle: That's a powerful reframe. It’s not about getting rid of the anxiety, but about welcoming it as a source of fuel. So what's the practical takeaway? How do we actually do this when we're in the middle of a panic? Mark: McGonigal offers a simple, three-step process. First, Acknowledge the stress. Notice it and accept that it's there. Don't fight it. Second, Welcome it. Remind yourself that the stress response is a sign that something you care about is at stake. And third, Use the energy. Instead of trying to calm down, ask yourself what you can do with the energy that stress is giving you. Michelle: I love that. It’s so active. It’s not about suppression; it’s about utilization. It reminds me of that story from the book about the woman who was listening to McGonigal's TED talk. Mark: Oh, that one gives me chills. She was sitting on her porch and heard a father next door physically abusing his child. She said that in the past, her own trauma would have made her freeze. But because she had just heard this idea of embracing the stress response, she thought to herself, "My body can give me the courage to act." And she called the police. Michelle: That's it right there. It’s not just about acing a test or a job interview. It’s about finding the capacity for courage in the moments that matter most. It transforms stress from a personal failing into a human resource.

Mark: That's the perfect way to put it. A human resource. The whole book is a journey to that realization. It starts with this radical idea that our beliefs can kill us or save us, and it ends with this deeply empowering toolkit for transforming our biology in real-time. Michelle: So, when we boil it all down, it seems the message isn't to seek out more stress or to ignore its very real dangers. It's about fundamentally re-engineering our relationship with the stress we will inevitably face in a meaningful life. Mark: Exactly. It's about recognizing that the feeling of a racing heart isn't a malfunction; it's your body giving you energy. The feeling of anxiety isn't a sign you're about to fail; it's a sign that you care deeply about the outcome. McGonigal calls this harnessing the 'biology of courage.' You're not broken when you feel stressed; you're activated. Michelle: And that shift from 'I'm broken' to 'I'm activated' feels like the whole game. It makes you wonder, what energy have we been misinterpreting as a threat? What could we achieve if we saw our own stress response as a resource, not a liability? Mark: That's a powerful question to leave our listeners with. And maybe a small challenge. Think of one stressful thing coming up this week—a tough conversation, a deadline, a family gathering. Instead of dreading it, try to see the physical sensations as your body gearing up to help you. Michelle: We'd love to hear how that goes. Let us know if you try it and what you discover. It’s a small shift with potentially huge implications. Mark: This is Aibrary, signing off.