I will never forget what it was like. The overwhelming misery. The certainty of never-ending suffering. No one to help you, no way to escape. Everywhere I looked: darkness so thick that the idea of light seemed inconceivable.

Suddenly, I swirled down a tunnel of fire, wailing figures calling out to me in agony, begging me to save them. Others tried to terrorize me. "You will never leave here," they said. "Never. Never."

I found myself laughing at them. "I'm not scared of you," I said. But the darkness became even thicker; the emotional charge of suffering nearly unbearable. I felt as if I would burst from heartbreak—everywhere, I felt the agony of humankind, its tragedies, its hatreds, its sorrows. I reached the bottom of the tunnel and saw three thrones in a black chamber. Three shadowy figures sat in the chairs; in the middle was what I took to be the devil himself.

"The darkness will never end," he said. "It will never end. You can never escape this place."

"I can," I replied.

All at once, I willed myself to rise. I sailed up through the tunnel of fire, higher and higher until I broke through to a white light. All darkness immediately vanished. My body felt light, at peace. I floated among a beautiful spread of colors and patterns. Slowly my ayahuasca vision faded. I returned to my body, to where I lay in the hut, insects calling from the jungle.

"Welcome back," the shaman said.

The next morning, I discovered the impossible: The severe depression that had ruled my life since childhood had miraculously vanished.

Giant blue butterflies flutter clumsily past our canoe. Parrots flee higher into treetops. The deeper we go into the Amazon jungle, the more I realize I can't turn back. It has been a year since my last visit, and I'm here again in Peru traveling down the Río Aucayacu for more shamanistic healing. The truth is, I'm petrified to do it a second time around. But with shamanism—and with the drinking of ayahuasca in particular—I've learned that, for me, the worse the experience, the better the payoff. There is only one requirement for this work: You must be brave. You'll be learning how to save yourself.

The jungle camp where our shamanistic treatment will take place is some 200 miles (322 kilometers) from the nearest town, Iquitos, deep in the Peruvian Amazon. Beside me are the other four members of my tour. There is Winston, the biggest person I've ever met. Nearly seven feet tall (two meters), surely over 400 pounds (181 kilograms), he has a powerful body that could easily rip someone apart. I expect him to be a bodyguard or a bouncer; turns out he's a security guard. But there is something else about him. Something less tangible. It seems to rest in the black circles beneath his eyes, the face that never smiles, the glances that immediately dismiss all they survey. Winston does not seem like a happy man.

Then the others: Lisa, who has a master's degree from Stanford and is now pursuing her doctorate in political theory at Duke University; Christy, who just quit her job counseling at-risk teens to travel around South America; and Katherine, Christy's British friend. By all appearances, our group seems to be composed of ordinary citizens. No New Age energy healers. No pan flute makers. No hippies or Rastafarians or nouveau Druids. Christy betrays only a passing interest in becoming a yoga instructor.

And then there is me, who a year ago came to Peru on a lark to take the "sacred spirit medicine," ayahuasca, and get worked over by shamans. Little suspecting that I'd emerge from it feeling as if a waterlogged wool coat had been removed from my shoulders—literally feeling the burden of depression lifted—and thinking that there must be something to this crazy shamanism after all.

And so I am back again.

I've told no one this time—especially not my family. I grew up among fundamentalist atheists who taught me that we're all alone in the universe, the fleeting dramas of our lives culminating in a final, ignoble end: death. Nothing beyond that. It was not a preion for happiness, yet, for the first couple decades of my life, I became prideful and arrogant about my atheism, believing that I was one of the rare few who had the courage to face life without the "crutches" of religion or, worse, such outrageous notions as shamanism. But for all of my overweening rationality, my world remained a dark, forbidding place beyond my control. And my mortality gaped at me mercilessly. Lisa shakes me from my reveries, asking why I've come back to take another tour with the shamans.

"I've got some more work to do," I say. Hers is a complicated question to answer. And especially personal. Lord knows I didn't have to come back. I could have been content with the results of my last visit: no more morbid desires to die. Waking up one morning in a hut in the sultry jungles of Peru, desiring only to live.

Still, even after those victories I knew there were some stubborn enemies hiding out in my psyche: Fear and Shame. They were taking potshots at my newfound joy, ambushing my successes. How do you describe what it's like to want love from another but to be terrified of it at the same time? To want good things to happen to you, while some disjointed part of you believes that you don't deserve them? To look in a mirror and see only imperfections? This was the meat and potatoes of my several years of therapy. Expensive therapy. Who did what, when, why. The constant excavations of memory. The sleuth-work. Patching together theory after theory. Rational-emotive behavioral therapy. Gestalt therapy. Humanistic therapy. Biofeedback. Positive affirmations. I am a beautiful person. I deserve the best in life.

Then, there's the impatience. Thirty-three years old already, for chrissakes. And in all that time, after all that therapy, only one thing worked on my depression—an ayahuasca "cleansing" with Amazonian shamans.