Chris Staniforth, a 20-year-old British "Xbox addict," died suddenly in May after a marathon session playing the Xbox game Halo. The untimely death prompted his father, David Staniforth, to launch a campaign warning other parents of the dangers of online video games. "Kids all over the country are playing these games for long periods," David says. "They don't realize it could kill them." Just how risky is marathon gaming?

What exactly killed Chris Staniforth?
A pulmonary embolism, or blod clot, that traveled from Staniforth's left calf to his lungs, causing a fatal blockage in a key artery. The clot was the result of deep-vein thrombosis (DVT), a condition that is usually associated with passengers on long-haul flights but can also be triggered when anyone sits in a static position for long stretches of time. Staniforth had a habit of playing "Halo" on his Xbox for up to 12 hours at a time.

Is it fair to blame gaming for his death?
It's a reasonable conclusion. Staniforth had no underlying medical conditions, and sitting for hours in front of a computer console is "pretty unhealthy, says Brian Colvin, an expert on blood-related conditions. Also, DVT rarely strikes someone as young as 20. David Staniforth says he's "not for one minute blaming the manufacturers of Xbox" for his son's death, since Microsoft discourages long stints in front of the console. But at the same time, "playing on it for so long is what killed him," David says, "and I don't want another child to die."

Is Staniforth the first known victim of marathon gaming sessions?
No. A South Korean gamer died in 2005 after playing online games for three days straight, with no breaks. And fatalities aside, "reports of gamers collapsing after spending 15 hours in front of video games are fairly common throughout Asia," says the AFP.

How big a problem is obsessive gaming?
The risk of dying is an issue but it "shouldn't be," says Naomi Brown in GamingExcellence. Parents should never let their underage kids sit in a single position playing games for hours on end, and "adults... are supposed to know when they've had too much of a good thing." All gamers should get up and stretch and walk around fairly frequently. "Video games are awesome, but you shouldn't have to die because you didn't know when to stop."

Sources: New York Daily News, AFP, BBC News, The Sun, GamingExcellence, Gawker, TechFlash