Nick Lotz believed that he was being tracked by TV cameras all day and all night. Photograph by AJ Frackattack

Soon after Nick Lotz enrolled at Ohio University, in the fall of 2007, he grew deeply anxious. He was overweight, and self-conscious around women; worse, he thought that everyone sensed his unease. People who once seemed like new friends gradually stopped returning his texts. He went out four or five nights a week, and drank to mask his discomfort, occasionally to the point of blacking out. After such episodes, he worried that he’d said, or typed, something that he should have kept private. He suspected that people were posting embarrassing videos of him online, though he couldn’t find any on Facebook.

Lotz, who wanted to be a filmmaker, largely ignored his classwork. Often, he’d draw the blinds of his dorm room and take Suboxone, an opiate that he bought from an older student, and sleep for days. Then he’d snort Adderall or Focalin and stay up all night, watching YouTube videos and working on screenplays. His laptop became his primary connection to the world. Online interactions were less taxing than face-to-face conversations, but they introduced new concerns: just as he monitored his friends’ Internet activity, he assumed that, whenever he clicked links on BuzzFeed or posted comments on Reddit, people were tracking him, too. When he surfed the Web, in a sleepless blur, every site seemed to contain a coded message about him.

In the spring, he returned home to Hudson, an affluent town between Akron and Cleveland. One evening, his mother, Ann, found him taking apart the thermostat in the front hallway. He was looking for cameras.

On another occasion, he told her that he was at the center of a network of covert operatives.

“Have you seen that movie ‘A Beautiful Mind’?” she asked.

“Mom, I’m not like that,” he said.

The next morning, he seemed more lucid, and he assured her that he was fine. School was stressful, and Adderall had aggravated the problem, but it wouldn’t happen again.

Lotz and his sister, Cecelia, had long-standing plans to attend a jam-band festival in western Michigan; their father, Jay, an event promoter, was travelling to the festival separately. Cecelia was concerned about Lotz’s state of mind, and told their parents that he should stay home, but he protested. His parents knew about his drinking and drug habits and were worried about him. They told him that he could attend the concert if he agreed to enter a rehab program, in Montana, immediately afterward.

Cecelia drove to the festival in their parents’ Volvo, with Lotz asleep in the passenger seat and three friends in the back. After the group pitched a tent, Lotz found a drug dealer and said, “Give me whatever I can get for a hundred dollars.” The next night, he took acid and Ecstasy. He and his friends hung out for a while, but eventually Lotz drifted, alone, toward the main stage. The headliner was the Dave Matthews Band, and, though Lotz did not love their music, he felt that he was there for a reason. He wedged his body closer to the stage. Matthews’s lyrics seemed eerily appropriate: “One year of crying and the words creep up inside.”

Suddenly, Lotz solved the puzzle of his life. Since starting college, he had been the star of a reality-TV show. The network had kept the cameras hidden, as in “Candid Camera” and “Punk’d.” That night was supposed to be the finale. All he had to do was call his father, who’d find him in the crowd, lead him onstage, and present him with a check for a million dollars. Lotz took out his cell phone, but he was too strung out to place the call. It was too late—he’d missed his chance to make the cameras turn off.

He returned to the tent and paced outside it until daybreak. When Cecelia woke up, she asked him what was wrong. He responded, “Smile, you’re on camera!”

The next day, he flew to Montana and began rehab. A counsellor, explaining the rules of the program, said, “We’re all going to be watching you.” To Lotz, this was an explicit acknowledgment that he was the star of a show that was being broadcast live, all day and all night. At the treatment center, he ducked into empty rooms, searching for editing equipment. He didn’t find any, but that proved nothing: cameras could be hidden behind mirrors or inside shirt buttons.

Lotz was discharged from rehab before he completed the program—his problems, the counsellors said, went beyond drug abuse. Back at home, he remained agitated, but he decided to keep quiet about the show. He completed a local rehab program, and declared himself ready for school. His parents, unsure what to do, allowed him to return to college for his sophomore year.

Lotz decided to embrace being watched by millions of strangers. He left his laptop open, allowing the cameras to zoom in on the screen, broadcasting his words to the world. When he spoke in class, he grinned clownishly, letting the audience know that he was in on the joke. He enrolled in acting and public-speaking courses, determined to become a better performer. Once, in acting class, he read an article about “the doubt or fatigue” that can wear down an actor. That night, Lotz wrote in his journal, “Anything that humiliates me or pisses me off is actually . . . a hazard of being famous.”

Psychotic disorders typically emerge between the ages of eighteen and thirty. One such condition, schizophrenia, affects approximately one per cent of the population, a figure that appears to have remained stable across epochs and continents. Hippocrates wrote of patients who exhibited paraphrosune, which translates roughly as “paranoia.”

Hypothetically, any false belief might turn into a delusion. You could become convinced that a Cézanne still-life contained real apples and pears. But in practice nobody suffers from Edible-Painting Delusion. Mental illness has rules. Just as all spoken languages share a universal grammar, clinically recognized delusions conform to a familiar set of themes, including persecution, grandiosity, and erotomania.

If form is fixed, content is not. Between 1995 and 2004, the International Study on Psychotic Symptoms, a survey of eleven hundred patients from seven countries, found that the mind supplies the contours of delusions, and culture fills in the details. Grandiose schizophrenics from largely Christian countries often claim to be prophets or gods, but sufferers in Pakistan, a Muslim country, rarely do. In Shanghai, paranoid people report being pricked by poisoned needles; in Taipei, they are possessed by spirits. Shifts in technology have caused the content of delusions to change over the years: in the nineteen-forties, the Japanese controlled American minds with radio waves; in the fifties, the Soviets accomplished this with satellites; in the seventies, the C.I.A. implanted computer chips into people’s brains.

For nine years, Joel Gold was the attending psychiatrist at Bellevue Hospital. “New York is a magnet for psychosis,” he says. “If someone loses it at J.F.K. or Grand Central, they’re brought right to Bellevue.” The delusions of Gold’s patients fell within standard categories, but the details often varied from those he’d read about in textbooks. “After 9/11, many Southern African-American women came to New York to raise the dead at Ground Zero,” he says. “You see that once and it’s, like, ‘Oh, interesting.’ Then, a week later, another one comes in.”