"We’re opening up the pearly gates!” Jonathan Grayson smiles when he says this, and his smile is contagious. Were it not, the nearly 100 conventioneers who have followed the doctor outside on this damply warm night in July would probably be fleeing for the safety of their sanitized hotel rooms. As they stand behind a Marriott a few miles north of Houston, the rickety door of a shed swings open and the nervous flock beholds what their smiling shepherd has brought them to see.

It’s a Dumpster. It’s full of food scraps. A fruity aroma of rot wafts up from its belly. “All those who’d like to get better,” Grayson bellows like a revival-tent preacher, “touch this!” They line up like congregants waiting for a warped sacrament. One by one they approach the Dumpster—wincing, clenching their jaws, even fighting back tears—and when they get to it, they smear their fingers and palms along its rim. “One whole finger,” a girl says proudly, holding it up, after she has passed through the fragrant sanctuary. “Oh, you can do better than that!” another woman tells her. “One whole hand!” She leads the girl back to the receptacle.

The bravest members of the throng stroke the Dumpster and run their fingers through their hair. A spasm of release washes over their faces. When everyone is done, Grayson rallies them again—“Come in closer! Everybody cross-contaminate!”—and they press together in the moonlight, arms draped over shoulders, in a germy group hug.

It’s safe to say the average human being would be repulsed by the idea of spending his Friday night communing with heaps of garbage, but for these folks even the prospect of a simple hug might be enough to induce paralysis. The people roaming the grounds of the Woodlands Waterway Marriott struggle with a mental illness that is estimated to afflict as many as one in 50 Americans, many of them exceptionally bright and ambitious: obsessive-compulsive disorder. Among them are hoarders and hand-washers, thermostat-checkers and symmetry-seekers, germ-avoiders and chronic fingertip-tappers, and they’ve come to Texas for this weekend’s 14th annual conference of the Obsessive Compulsive Foundation.

Thanks in part to pop-culture depictions such as The Aviator, As Good As It Gets, and Monk, the source of their torment has become oddly chic these days. OCD has become a catch-all term for anal-retentive fussiness—“Dude, I always save my receipts from the ATM, I’m sooo OCD!”—when in fact the people who endure its maddening headspace despotism might as well be locked down in a maximum-security prison. Traveling to a gathering of fellow sufferers, then, is like going on a psychic furlough. This is the first time some of them have ever met, let alone hugged, let alone swapped microbes with, anyone else laid low by their strange and stubborn disorder.

Dr. Grayson, who runs the Anxiety and Agoraphobia Treatment Center, outside Philadelphia, and published the book Freedom from Obsessive-Compulsive Disorder in 2003, represents the cutting edge of a practice known as exposure therapy, and his Willy Wonka-style romp through germland will be, for many, the habit-shattering highlight of the weekend. The Dumpster is only part of it. OCD comes in many varieties; not everyone who has it is afraid of contamination. Some are fixated on the irrational thought that they’re going to hurt someone. They might even booby-trap their own homes so that they don’t wake up in the middle of the night and murder their kids. Some are fanatical pack rats, cramming their homes with ziggurats of clutter. Some lust for order and can’t stand to see a single button out of place. Grayson, who is gray-bearded and extroverted and, at 55, looks as though he could have once been a Doobie Brother, has an “exposure” for each one—a moment when they’re encouraged to confront the thing they fear.