In September, an 11-year-old boy who had just entered sixth grade in South Carolina died alone in his bedroom playing what many call "the choking game."

In early March, a student at Hillview Middle School in Menlo Park ended up with a broken jaw while involved in a variation of the same activity, with a group of students on the school's playing field at lunchtime.

In a 2008 study, the federal Centers for Disease Control documented 82 deaths attributed to the "choking game" between 1995 and 2007, one of them of a 6-year-old. The game, experts say, has many allures for children, yet most of them do not realize how dangerous it is.

The lack of oxygen leads to a brief euphoric feeling, or "high," however the same lack of oxygen can cause brain damage, seizures, or death, the CDC report says.

Those involved often hyper-ventilate and then either try to cut off further air intake by strangulation with hands or a noose, or by having someone sit on their chest, the CDC report says.

NoBullying.com says: "Children and teens are unaware of how quickly they can pass out and that the more they play the game, the longer they will have to be strangled to achieve the desired high."

Talk to kids

Devin Prouty, a licensed clinical psychologist who works with adolescents and is a researcher at SRI in adolescent brain development, said talking about the dangers of this behavior "is probably the most protective thing you can do for your kids."

Mr. Prouty, a resident of Menlo Park and the father of an 11- and 13-year-old, said he "talked to my kids about it as soon as I heard about it." He recommends asking children what they know about the game and sharing with them the dangers.

Hillview Assistant Principal Danielle O'Brien suggested a similar thing in a note she sent to school parents after the incident at the school.

"The most impactful action we can take as adults in our students' lives is to engage in conversation and ask questions," she wrote.

Mr. Prouty suggested the Wikipedia choking game entry as a good source of facts and physiology that "would be good reading for our kids."

"Your kids may be smart and intelligent and informed, but they may still misunderstand this and think it's completely harmless," he said.

Why they do it

Mr. Prouty said children take part in such activities for "a lot of reasons." Children between 12 and 15 are the most likely to take part. They are working on becoming independent and often practicing thrill-seeking and risk-taking behavior and other experimentation, he said.

"There's also a social component to the game," he said. They "just want peer acceptance."

"For some kids, it can be seen as sort of a dare," he added. "Doing things to impress their peers and sort of be with the 'in' group."

Children of this age have undeveloped frontal brain lobes, which he called "the seat of reason."

"Kids of this age will take risks," he said. "Their brains are still developing and they're still working out the balance between impulse control and decision-making."

"I wouldn't think for any kid, it's any one thing," he said. "The allure of 'getting high' could be powerful to these kids," he said. What they don't realize, however, is that this oxygen deprivation can be "more dangerous than smoking marijuana," he said.

When to seek help

Some of the research indicates that children who take part in the activity alone, often in their bedroom at home, may have more serious mental health issues. The CDC study said 95 percent of deaths were of children who were alone.

"If your child is doing this alone, you really want to talk to the pediatrician and maybe look into more intense support for this child," Mr. Prouty said.

The New York State Department of Health website says the following are symptoms that a child may be involved in a pass-out activity: bloodshot eyes, frequent and severe headaches, unexplained marks on the neck, pinpoint bleeding spots under the skin on the face or eyelids, disorientation after spending time alone, increased and uncharacteristic irritability or hostility, wearing high-necked shirts even in warm weather, finding ropes, scarves or belts tied to bedroom furniture or doorknobs, or the unexplained presence of things such as dog leashes, chock collars or bungee cords.

The health department's website says that "after just a few seconds of choking, children may pass out. This can lead to serious injury or even death from hanging or strangulation. Within three minutes of continued strangulation, basic functions such as memory and balance start to fail. If this happens, death can occur shortly after."