By Thomas Fields-Meyer
Updated August 22, 2005 12:00 PM

Tammy and Joe Dunn thought their daughter Chelsea was having a typically rocky transition into her teens. The Nampa, Idaho, 13-year-old had previously posted solid grades. But last winter she started failing her classes. She also grew increasingly reclusive. When the rest of the family went out to eat, she stayed home, spending hours alone in her room. When the Dunns inquired into her performance at school, her counselor, recalls Joe, said, “she was just being a kid—testing her boundaries.”

If only the family had known how much. On April 14, when Chelsea didn’t come to breakfast, Joe sent her twin brother, Hunter, to check on her. He came out of his sister’s room sobbing hysterically. “My first thought was, ‘Did she run away?'” says Tammy, 36. “Then Joe went up and I heard him screaming.” He had found Chelsea hanging from her closet door, a belt and shoelace tied around her neck, lifeless. Says her mother: “I just kept thinking, ‘I can’t believe this is happening.'”

The police have not fully ruled out suicide. But the true cause of Chelsea’s death may be even more incomprehensible. Her parents believe that Chelsea accidentally strangled herself in an effort to attain a drug-like high. The practice of cutting off oxygen in an effort to increase sexual pleasure has been a known problem with older youths and adults for some time. But this was different. This was a game played by children and spread via chat rooms and word of mouth. Sometimes called space monkey, flatliner or blackout, the practice is responsible for the deaths of a number of children across the country. “This is extreme risk-taking,” says University of California, San Francisco, child psychiatrist Dr. Lynn Ponton. “They are flirting with death.”

While kids have been experimenting with holding their breath and hyperventilating for centuries, psychologists and law enforcement officials say some are now taking such slumber-party play to new extremes, employing belts, plastic bags, ropes and bedsheets to make themselves pass out. When they come to, they supposedly experience a euphoric feeling, as oxygen rushes back to the brain. “I love that pass-out thing,” Chelsea wrote in a note her parents found in her makeup bag. “You forget everything, and it comes back to you and it’s all tingly.”

Gabriel Mordecai, 13, of Paradise, Calif., seems to have died pursuing the same feeling. His mother, Sarah Pacatte, a preschool teacher, knew her son and his twin brother, Samuel, were experimenting with the pass-out game and had warned them about it. “I said, ‘This is stupid,'” says the single mom of four. “‘You can die from this.'” The boys promised to quit. But on May 5, Pacatte was helping Samuel with a science project in one room while in another Gabriel was tying a rope around his own neck. Discovered unconscious by his brother, he died the next day. Now Pacatte is haunted by what Gabriel once told her about the game: “He said, ‘What’s the big deal? It’s not like we’re doing drugs.'”

In fact, say child psychiatrists, many of the kids experimenting with suffocation are trouble-free youths unlikely to try illegal narcotics. “The game is immediately accessible,” says Dr. Ashraf Attalla, an Atlanta child psychiatrist. “They can do this to themselves immediately.” Usually the game involves at least two children, one to help stop the choking. But cutting off oxygen to the brain even briefly can cause severe injury and death—a danger that multiplies when a kid tries the game alone. “They don’t know where the threshold is where people could die,” says Temple University psychologist Frank Farley. A growing number of doctors and officials are alerting parents and children to the dangers of this game, but warning signs can be subtle (see box). Until recently most coroners concluded that kids found dead from self-strangulation were suicides. Now New Hampshire chief medical examiner Dr. Thomas Andrew suspects many such deaths are accidents related to the game. “The evidence,” he says, “looks exactly the same.”

Many participants are simply misjudging the risks. Patricia Eby realizes that’s what happened to her son Dal-ton, a cheerful 10-year-old who excelled in gymnastics. On July 7 he set out for a bike ride from their Island Park, Idaho, home and didn’t return. After a two-day search, sheriff’s deputies discovered Dalton’s body in a tree house in the nearby woods. A rope was tied around his neck. Investigators quickly concluded that he had been trying to choke himself after learning of the game from peers. “Dalton thought it was a game—that he would just pass out,” says Patricia, 41, who runs a lodge with her husband, Dave. “He didn’t know he would die.”

Neither, apparently, did Chelsea Dunn. It was only after her death that her parents discovered their child—who loved drawing and the violin—had been playing the game with friends. “We made sure to talk to her about drugs, smoking and alcohol,” says Tammy Dunn. “We hadn’t been told anything about this.”

Thomas Fields-Meyer. Vicki Sheff-Cahan and Frank Swertlow in Los Angeles, John Perra in Washington, D.C., and Nicole Weisensee Egan in Philadelphia