In the late 1990s, an unusual experiment took place in the trauma center of a hospital in Akron, Ohio. Patients who had just survived a major car or motorcycle accident were asked to pee into a cup. These urine samples were part of a study on posttraumatic stress disorder (PTSD). The researchers wanted to know: Can you predict who develops PTSD based on their level of stress hormones immediately after the trauma?

One month after their accidents, nine of the 55 patients were diagnosed with PTSD. They had flashbacks and nightmares. They tried to avoid reminders of the accident by not driving, staying off highways, or refusing to talk about what happened. Yet 46 patients were not suffering in the same way. These more resilient patients had a different post-accident pee profile than the patients who developed PTSD. They had higher levels of the stress hormones cortisol and adrenaline.

Cortisol and adrenaline are part of what scientists call the stress response, a set of biological changes that help you cope with stressful situations. Stress affects many systems of your body, from your cardiovascular system to your nervous system. Although the purpose of these changes is to help you, the stress response, like stress more generally, is more feared than appreciated. Most people view the stress response as a toxic state to be minimized, but the reality is not so bleak. In many ways, the stress response is your best ally during difficult moments—a resource to rely on rather than an enemy to vanquish.

The study of accident survivors at the Akron, Ohio, trauma center was just the first of several studies showing that a stronger physical stress response predicts better long-term recovery from a traumatic event. In fact, one of the most promising new therapies to prevent or treat PTSD is administering doses of stress hormones. For example, a case report in the American Journal of Psychiatry describes how stress hormones reversed posttraumatic stress disorder in a 50-year-old man who had survived a terrorist attack five years earlier. After taking 10 milligrams of cortisol a day for three months, his PTSD symptoms decreased to the point that he no longer became extremely distressed when he thought about the attack. Physicians have also begun to administer stress hormones to patients about to undergo traumatic surgery. Among high-risk cardiac surgery patients, this approach has been shown to reduce the time in intensive care, minimize traumatic stress symptoms, and improve quality of life six months after surgery. Stress hormones have even become a supplement to traditional psychotherapy. Taking a dose of stress hormones right before a therapy session improves the effectiveness of treatment for anxiety and phobias.

Rising to the Challenge

As the renowned Harvard physiologist Walter Cannon first observed, a fight-or-flight stress response starts when your sympathetic nervous system kicks in. To make you more alert and ready to act, the sympathetic nervous system begins to direct your whole body to mobilize energy. Your liver dumps fats and sugars into your bloodstream for fuel. Your breathing deepens, to deliver more oxygen to your heart. Your heart rate speeds up to deliver the oxygen, fat, and sugar to your muscles and brain. Stress hormones like adrenaline and cortisol help your muscles and brain take in and use that energy more efficiently. In all of these ways, your stress response gets you ready to face whatever challenges lie in front of you.

When this part of the stress response kicks in, it can give you extraordinary physical abilities. There are countless news reports of so-called “hysterical strength” attributed to stress, including the story of two teenage girls in Lebanon, Oregon, who raised a 3,000-pound tractor off their father, trapped underneath. “I don’t know how I lifted it, it was just so heavy,” one of the girls told reporters. “But we just did it.” Many people have this kind of experience during stress: They don’t how they found the strength or courage to act. But when it matters most, their bodies gave them the energy and will to do what was necessary.

The energy you get from stress doesn’t just help your body act; it also fires up your brain. Adrenaline wakes up your senses. Your pupils dilate to let in more light, and your hearing sharpens. The brain processes what you perceive more quickly. Mind-wandering stops, and less important priorities drop away. Stress can create a state of concentrated attention, one that gives you access to more information about your physical environment.

You also get a moti-vation boost from a chemical cocktail of endorphins, adrenaline, testosterone, and dopamine. This side of the stress response is one reason some people enjoy stress–it provides a bit of a rush. Together, these chemicals increase your sense of confidence and power. They make you more willing to pursue your goals and approach whatever is triggering the flood of feel-good chemicals. Some scientists call this the “excite-and-delight” side of stress. It’s been observed both in skydivers falling out of planes and people falling in love. If you get a thrill out of watching a close game or rushing to beat a deadline, you know this side of stress.

When your survival is on the line, these biological changes come on strong, and you may find yourself having a classic fight-or-flight response. But when the stressful situation is less threatening, the brain and body shifts into a different state: a challenge response. Like a fight-or-flight response, a challenge response gives you energy and helps you perform under pressure. Your heart rate still rises, adrenaline spikes, and your muscles and brain get more fuel. The feel-good chemicals surge. But in a few important ways, it differs from a fight-or-flight response. You feel focused but not fearful. You also release a different ratio of stress hormones, including higher levels of DHEA, which helps you recover and learn from stress.

People who report being in a flow state—a highly enjoyable state of being completely absorbed in what you are doing—show clear signs of a challenge response. Artists, athletes, surgeons, video gamers, and musicians all show this kind of stress response when engaged in their craft or skill. Contrary to what many people expect, top performers in these fields aren’t physiologically calm under pressure—they have strong challenges responses. The stress response gives them access to their mental and physical resources, and the result is increased confidence, enhanced concentration, and peak performance.

Encouraging Connection

Your stress response doesn’t just give you energy. In many circumstances, it motivates you to connect with others. This side of stress is primarily driven by the hormone oxytocin. Oxytocin has gotten a lot of hype as the “love molecule” and the “cuddle hormone” because it’s released from your pituitary gland when you hug someone. But oxytocin is a much more complex neurohormone that fine-tunes your brain’s social instincts. Oxytocin’s primary function is to build and strengthen social bonds, which is why it’s released during breastfeeding, sex, and hugs. Elevated levels of oxytocin make you want to connect with others. It creates a craving for social contact, be it through touch, a text message, or a shared beer. Oxytocin also makes your brain better able to notice and understand what other people are thinking and feeling. It enhances your empathy and your intuition. When levels of oxytocin are high, you’re more likely to trust and help the people you care about. Oxytocin even amplifies the warm glow you get from caring for others, by making the brain’s reward centers more responsive to social connection.

But oxytocin isn’t just about social connection. It’s also a chemical of courage. Oxytocin dampens the fear response in your brain, suppressing the instinct to freeze or flee. This hormone doesn’t just make you want a hug. It also makes you brave.

Sounds like a good hormone, right? Some people have even suggested we snort it to become better versions of ourselves. You can actually buy oxytocin inhalers online. But oxytocin is as much a part of your stress response as the adrenaline that makes your heart pound. During stress, your pituitary gland releases oxytocin to motivate social connection. That means stress can help you be this “better” version of yourself, no snorting required.

When oxytocin is released as part of the stress response, it’s encouraging you to connect with your support network. It also strengthens your most important relationships by making you more responsive to others. Scientists refer to this as a tend-and-befriend response. Unlike the fight-or-flight response, which is primarily about self-survival, a tend-and-befriend response motivates you to protect the people and communities you care about. And, importantly, it gives you the courage to do so.

When all you want is to talk to a friend or a loved one, that’s the stress response encouraging you to seek support. When something bad happens, and you think about your kids, your pets, your family and friends—that’s the stress response, encouraging you to protect your tribe. When somebody does something unfair, and you want to defend your team, your company, or your community, that’s all part of this prosocial stress response.

Protecting Your Heart

Oxytocin has one more surprise benefit: This so-called love hormone is actually good for cardiovascular health. Your heart has special receptors for oxytocin, and oxytocin helps heart cells regenerate and repair from any micro-damage. When your stress response includes oxytocin, stress can literally strengthen your heart. Quite different from the message we usually hear, that stress will give you a heart attack! There is such a thing as a stress-induced heart attack, typically triggered by a massive adrenaline surge, but not every stress response damages your heart. In fact, one of the most provocative studies I’ve seen found that stressing out rats before inducing a heart attack actually protected them from heart damage. When researchers gave the rats a drug that blocked oxytocin release, stress no longer protected their hearts. This study hints at one of the most surprising sides of stress. Your stress response has a built-in mechanism for resilience—one that motivates you to care for others, while strengthening your physical heart.

13 Reasons to Love Stress

Stress hormones can …

1. Concentrate your attention

2. Increase your confidence

3. Improve your physical strength

4. Enable you to see better

5. Enable you to hear better

6. Help during traumatic surgery

7. Improve treatment for anxiety

8. Protect against posttraumatic stress disorder

9. Make you more social

10. Help you protect your family

11. Create the experience of flow

12. Protect your heart

13. Make you feel great