The panic grew with every move I made: gripping small handholds with suddenly sweaty palms, placing my soft rubber-soled climbing shoes onto small ledges and nubs in the granite face. My chest seized up; the fear gripping my lungs and my brain made me dizzy. I breathed loud and fast through my mouth. My brain screamed warnings at my body:

It was an early May evening at the Rock Gardens, a popular climbing crag in Whitehorse, the small capital city of the Yukon Territory, where I live. By attempting to climb a steep stone wall, I was deliberately terrorizing myself, creating a situation I knew would induce something similar to a panic attack. But if I could learn to be less afraid while harnessed up and clinging to a rock face, I had decided, I might learn to control my debilitating fear of heights more generally.

Amber Xu

That night, I managed to force my way six or seven feet up a twenty-six-foot route before I begged my climbing partner, belaying me from below, to lower me down. As my feet touched the ground, I tried to control my panting and avoided looking anyone in the eye.

Acrophobia, or extreme fear of heights, is among the most common phobias in the world: One Dutch study found that it affects as many as one in twenty people. Even more people suffer from a non-phobic fear of heights—they don't meet the bar to be technically diagnosed, but they share symptoms with true acrophobes like me. All told, as much as twenty-eight percent of the general population may have some height-induced fear.

Plenty of people work around acrophobia, simply avoiding triggering situations. But seven and a half years ago, I moved to the Yukon, where many people spend their time hiking up steep mountains, climbing rock walls and frozen waterfalls, pinballing down mountain biking trails. My fear became a true liability—an obstacle between me and new friends, new hobbies, a new lifestyle. During my first full summer in Whitehorse, I panicked twice on hiking trails, curling up on the ground and refusing to move at all, or creeping along Gollum-like, on all fours, while everyone around me walked upright. It was intolerable.

So last summer, I formulated a plan: I'd use the latest research to build myself a DIY cure—or, at the very least, a coping mechanism. I was going to master my fear by exposing myself to it, over and over again.

"Face your fears" is an old idea. Even its modern, clinical variation—the idea that, as a 1998 paper in the Journal of Consulting and Clinical Psychology put it, "emotional engagement with traumatic memory is a necessary condition for successful processing of the event and resultant recovery"—dates back more than a century, to the work of Pierre Janet and Sigmund Freud. But its codified, therapeutic application is much more recent, and it has important implications not just for people with phobias, but those dealing with all sorts of anxiety-based conditions, from obsessive-compulsive disorder to PTSD. Facing one's fears, done correctly, could be a way forward for tens of millions of people whose anxieties control them.

I based my goals and methods of my DIY therapy program on the concept of "exposure therapy," a concept that owes its existence largely to Israeli psychologist Edna Foa, now the director of the University of Pennsylvania's Center for the Treatment and Study of Anxiety. As a post-doctoral fellow at Temple University in the early 1970s, Foa trained under Dr. Joseph Wolpe, the father of what was then known as systematic desensitization. Wolpe's work involved exposing phobic or anxious patients to the sources of their fears, mostly using "imaginal" exposure—for instance, having an arachnophobic patient imagine a spider at a distance, and then imagine the spider slightly closer, and so on—combined with relaxation techniques.

Foa's innovation was investigating whether a greater degree of "in vivo" exposure—exposure to the real fear stimulus, not just an imagined one—could improve on Wolpe's promising results. Earlier researchers had assumed such direct exposure could be dangerous for patients with phobias and anxiety disorders, but the science on that front was changing. "I started to do studies of exposure in vivo, starting not with the highest level of fear but with moderate levels, and going faster, proceeding to higher and higher situations that evoke higher and higher anxiety," Foa told me. The results, she said, were "excellent."

Exposure therapy is basically an inversion of a well-known psychological technique known as classical conditioning. If you can teach an animal to expect pain from, say, a blinking red light by repeatedly combining the light's appearance with an electrical shock until the animal reacts fearfully to the light alone, it makes sense that the twinning of stimulus and fear can be unraveled too. Show the animal the red light enough times without an accompanying shock, and eventually it will no longer fear the light—a process known as extinction. I was determined to extinguish my fear by proving to myself that I could climb a cliff.

Amber Xu

If I was afraid of heights as a small child, I don't remember it. I never climbed trees, and I was uncomfortable when my friends and I clambered up to sit on top of the monkey bars on the playground. But I was a timid kid in general—I once told my mom that I never ran as fast as I could in school races, for fear of losing control and falling—so all that was of a piece with my personality at that time.

In my first clear memory of feeling afraid of heights—not just afraid, but terrified—I am fifteen years old. It was the summer after ninth grade, and I'd signed up to spend a week sailing on an old-fashioned ship on Lake Ontario with a dozen other teens. I loved everything about life on board that ship: sleeping in my narrow metal bunk below deck; waking in the middle of the night to stand watch, peering out at the endless darkness; lounging on sunny afternoons in the net that hung below the carved bow. On deck, we wore harnesses around our chests, fitted with a short rope ending in a heavy metal clip. In very rough weather, or if we were climbing the mast to adjust the sails, we were meant to clip ourselves in, just in case.

The problem came the first time I tried to climb the mast—to "go aloft," in sailing terminology. I got partway up, moving my clip as I went, fighting panic with each step on the ladder-like holds. Then I froze. I couldn't stop staring at the wooden deck swaying below me, couldn't stop picturing my body splattering against it, my bones shattering, my blood running into the lake.

The ship's "officers"—our camp counselors—managed to coax me down, and I never went aloft again. Everyone was kind to me about my failure, but there was no point in coming back the following year. A sailor who can't adjust the sails in a pinch isn't much use.

After that, my fear went dormant again for nearly a decade. It resurfaced after grad school, while I was backpacking with friends in Europe. I'd developed a fascination with the art and architecture of old churches, and we hit cathedral after cathedral across the southern half of the continent. We visited a few cupolas, and I gritted my teeth going up and down the narrow stone stairways. But I didn't truly panic until Florence.

I'd made it to the top of the legendary Duomo and was breathing deeply, trying to stay calm and enjoy myself as I looked out over the city's terracotta rooftops. The famous steep red dome of the cathedral curved away below me, and as I glanced down at it, suddenly all I could think about was how it would feel to tumble over the flimsy metal railing in front of me, to slide down over those red tiles toward the drop-off. I couldn't breathe.

The viewing platform was crowded with tourists. I pushed through them to the wall and slid down with my back against it, put my head between my knees to block out the view, and hyperventilated through my tears. My friends found me there, eventually talked me to my feet, and held my hands while we inched back down the twisting staircase to safety and solid ground. We didn't visit any more cathedral towers after that.

Ivy Yeh

In the years since that humiliating incident, I've tried to figure out why I react to heights—specifically exposed heights; I'm generally fine in enclosed spaces, like elevators and airplanes—the way I do. Phobias can often derive from traumatic experiences, or even observations of others' traumatic experiences, early in life. But it turns out that the acrophobia is different. If I'm anything like the subjects of recent research, I have measurably sub-par control over my body's movement through space, as well as an over-dependence on visual cues—which are distorted by heights—to manage my movement through the world. In other words, I am afraid of falling from heights because I am more likely than other people to fall from heights.

For a 2014 paper in the Journal of Vestibular Research, a team of German scientists studied the eye and head movements of people who are afraid of heights, plus a control group, as they looked over a balcony. They found that their fearful subjects tended to restrict their gazes, locking their heads in place and fixing their eyes on the horizon rather than looking down or around at their surroundings. That description will ring true to anyone who's ever felt afraid of heights, or tried to counsel someone who is: Don't look down. Whatever you do, don't look down.

So, ironically, I fix my gaze to the horizon as a defense mechanism against my fear, but because that fear is rooted in my over-reliance on visual cues, restricting my range of vision can only make things worse. It's a cycle: My brain knows that my body is bad at navigating heights, so it sends out fear signals as a warning. My body shuts down in response, which only increases the likelihood that I will actually harm my klutzy self. And thus a once-rational response to a reasonable concern feeds on itself, growing and spreading to the point where I can hardly stand on a sturdy stepladder.

A few weeks after that first outing in May, I was back at the Rock Gardens. I'd been making sporadic attempts to face my fears for years, but now I intended to be more systematic about my efforts, and to document them as I went.

Ivy Yeh

The route I was attempting was a beginner's climb, laughably easy for most people with any experience. And it came with a cheat option: a detour of a few feet to the right, into a wide crack between two rock faces made it even simpler. But to get to the crack and the easiest way up, I had to make one slightly tricky move. I would have to step forward with my left foot, balance the toe of my shoe on a small nub, shift all my weight briefly to that left toe, then swing my right foot over and across to the next proper ledge—all without any handholds for balance.

My climbing partner stood below me, holding the other end of the rope that secured me to the bolted metal anchors at the top of the climb. If I fell, she would pull down on the rope, stopping me before I'd plummeted more than a foot or two. Climbing on top rope, as it's known, involves almost no real risk. But my lungs constricted anyway, and I fought to squelch my dizziness and panic. From the ground, my friends encouraged me: Trust your shoes, trust your feet. This will be fine. You can do this.

Finally, I took a deep breath, stepped forward, shifted my weight from one foot to the next and made it across. I fumbled above my head for handholds to steady myself, then grinned and tried to breathe. For a moment while I was in motion, I had felt weightless, in control. Unafraid. Now the fear came seeping back as I continued climbing, scrambling through the loose dirt that had collected on the ledges and lumps of rock in the crack. I finished the climb, but raggedly, fending off panic the whole way. It was a good start, but as my belayer lowered me back down to the ground, I knew I had a long way to go.

We don't know exactly what happens in the brain during the extinction process. As Foa puts it, "is it that you erase the connections" between stimulus and fear, "or that you replace them with a new structure?" Her hypothesis is that exposure therapy trains the brain to create a second, competing structure alongside the traumatic one. The new structure, she explained, "does not have the fear, and does not have the perception that the world is entirely dangerous and that oneself is entirely incompetent."

That was why my panicked success in the Rock Gardens that day was really no success at all. I had climbed the wall, sure, but I had failed to convince my brain to build a new structure. Repeatedly terrorizing myself wouldn't solve my fear; it wasn't enough to scramble through with wild eyes and a pounding heart. I had to learn to stay calm.

Perhaps the most transformative application of exposure therapy is using it not to combat specific phobias, or even broader anxiety-based disorders, but post-traumatic stress disorder. In 1980, PTSD was included for the first time in the Diagnostic and Statistical Manual of Mental Disorders. In the decades since, our understanding of the disorder has grown, and so has our grasp of its staggering reach. We now know that PTSD affects not just soldiers and civilians emerging from war, but also drone operators who've never left their home base; first responders from beat cops to search-and-rescue volunteers operating out of luxurious mountain resorts; survivors of car wrecks, assaults, and less obvious forms of trauma.

But back in the early 1980s, "we didn't have any studies on PTSD," Foa said. "And I thought, well, this is an anxiety disorder, there is no reason why we cannot adapt the treatment, the exposure therapy treatment, to PTSD." You can't re-expose someone to a rape or a bomb, so Foa settled on a program of imagined exposure for the traumatic memory itself, but in vivo exposure to the secondary effects: the patient's avoidance behaviors, which can perpetuate trauma's power. In sessions with therapists, patients would confront the memory using imaginal exposure. Their "in vivo" exposure came as homework: going to places that reminded them of the trauma, or to safe places they perceived as dangerous. Sometimes that meant walking a downtown street at night after a violent assault, or going to malls again after a mass shooting.

Throughout the 1990s, Foa's team taught others groups of therapists how to administer what she called prolonged exposure therapy (or PE), and how to monitor the results. They found that PE was effective in almost eighty percent of patients: Between forty and fifty percent became essentially symptom-free, while twenty to thirty percent still had some recurring symptoms but were much improved. "We're not 100 percent successful," she said, "but no treatment is." She launched PE into the wider world with a series of papers in the late '90s, and within a few years the program had become the gold standard for treatment of anxiety disorders and PTSD. In 2010, Foa was named one of Time's 100 most influential people. "No one is doing more" to end the suffering caused by PTSD, the magazine declared.

An estimated eight million American adults experience PTSD every year. Nineteen million more deal with specific phobias, six million with panic disorders, seven million with generalized anxiety disorder, and more than two million with OCD. The Anxiety and Depression Association of America estimates that only one-third of anxiety-disordered patients receive treatment. Now, researchers are exploring whether pharmaceuticals can enhance the effectiveness of exposure therapy, while others have applied variations of PE to grief, depression, eating disorders, and beyond.

Compared to living with PTSD or broader anxiety disorders, my fear of heights is trivial. It doesn't keep me awake at night, or ruin my relationships, or bleed into every area of my life. If I moved back to the flatlands and avoided high-rise balconies, dodging my symptoms by practicing avoidance, I would hardly notice it.

Still, it can limit me. I would have liked to climb that mast high into the rigging, to enjoy the view over Florence. Sometimes I get scared on bridges or balconies, and I have still never climbed a tree. Taken individually those are all tiny things, but they add up to a feeling of helplessness: My choices are not entirely my own.

The rock was cold enough to numb my fingers. It was October 2, and I was on my eighth and final climbing excursion of the season, before winter set in. All summer, I had gone climbing every time someone with the necessary expertise and gear was willing to take me along. I had tried to systematize my outings, repeating the same routes to see if I could get farther, and stay calmer, each time.

In previous years, I would have pushed myself until my panic was unbearable, hoping that I could pop it like a soap bubble if only I tried hard enough. But now my strategy was to go only as far up as I could without paralysis setting in. The goal was to build up the alternate structure in my brain that said "This is okay. You are safe," then come down before the old structure could assert itself, and hope to get a foot or two farther next time around.

For this last outing, three friends and I were at Copper Cliffs, a crag in Whitehorse's semi-industrial backyard: once a booming copper mining area, now a maze of quarries and mountain biking trails and small, shallow lakes. I was climbing Anna Banana, a short, beginner-friendly, sixteen-foot route up one side of an arête, a sharp wedge of rock protruding from the main cliff face. My first steps had been on easy footholds, gaps cutting into the leading point of the wedge, and I had no trouble until my feet were seven and a half, eight feet off the ground. I stalled out there, my right foot resting on a good ledge just around the corner of the arête while my left toe was tucked into a little cubbyhole a foot below. To continue, I had to pull my left leg up several feet, to the next good hold.

I raised my arms and patted the rock above my head, blindly seeking out handholds that I could use to pull myself up higher, to give my left foot a fighting chance. I tend to trust my hands and arms first, even though my legs are exponentially stronger: We're less accustomed to trusting a narrow toehold than a fist clamped around something solid. But I didn't find what I was looking for, so instead I spread my arms out wide and locked my fingers around the best stabilizing holds I could reach. Then I pushed off with all my weight on my right foot, pulled my arms tight to keep me close to the rock face, and scraped my left foot up the wall until I found the next hold, just as my right toe lost contact with the rock. I balanced there for a moment, then raised my hands to holds suddenly within my reach and pulled up my dangling right foot.

I had done it. More importantly, I had done it calmly and coolly, without needing extra minutes to fight off panic, without groaning and moaning before I gave it a try. My belayer lowered me down so I could climb up and do it again—more confidently, with even less hesitation. This time I kept going, through a series of easy moves to the top of the route, where I reached up and smacked the anchor bolts in triumph: a touchdown spike. I did a quick mental survey of my body: My breathing was steady, my head clear. For today, at least, I had successfully re-directed my brain to reject fear.

Months later, I'm still working on training my brain. I've kept climbing through the winter, at big indoor gyms in San Francisco and Vancouver and on small, homemade climbing walls here at home; in local schools and in a friend's basement. By my standards, I've made substantial progress. These days my chest doesn't constrict and my pulse doesn't start to pound in my ears until I'm much higher off the ground: six, eight, ten feet. Sometimes I can complete an entire short route without feeling afraid at all.

I've started applying the basic ideas behind exposure therapy in other areas of my life, too. So often, whether in our careers or our athletic endeavors or even our love lives, we're encouraged to "take the plunge," to "push our limits," to "go big or go home." But my DIY climbing therapy has taught me the value of care, of caution, of building up your abilities and endurance slowly to reach a larger goal. Taking the plunge has its place, but sometimes it's enough to immerse yourself toe by toe.

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