Internet addiction is becoming a huge problem in China. As ever-larger numbers of teens and young adults spend ever more time at cyber-cafes playing games and exploring online worlds, they are spending less and less time AFK, with a frightening number of people skipping school and even sleep. To combat the problem, a handful of rehabilitation centers have popped up to treat the growing ranks of urban youth identified as internet addicts.

Filmmakers Shosh Shlam and Hilla Medalia went into a treatment center in the Beijing area for Web Junkie, a documentary premiering this weekend at the Sundance Film Festival. They wanted to spent time with the people sent there, and learn more from the people who treat them. They found that most of the young people classified as web addicts – a clinical assessment that is fairly common in China but has not yet found its way into the Diagnostic and Statistical Manual of Mental Disorders – had spent so much time online that they believed the virtual world was more engaging and more real than the real world. That led many of them to disengage socially.

A young man named Wu Huhu explains in the film that he once spent some 300 hours – nearly 24 hours a day for 15 days – in an marathon session playing World of Warcraft. Another young man chimes in to reminisce about spending an entire summer break playing the game. It's a jovial exchange between a bunch of kids with a shared experience, but also a haunting lesson in why web addiction is taken so seriously in China.

Internet abuse – and the web in general – will be a popular theme at Sundance this year. In addition to Web Junkie, the documentary Love Child examines the case of a South Korean couple whose baby died in 2010 while they were gaming at an internet cafe. The Internet's Own Boy: The Story of Aaron Swartz looks at the impact of the young internet activist who died a year ago, and the narrative film The Signal tells the story of two MIT students who follow a rival hacker's clues and find themselves imprisoned. The lineup of films shows just how much the internet has become an integral part of many of the best stories.

More on the web's impact on the Sundance Film Festival coming soon. In the meantime, check out the entire World of Warcraft conversation in an exclusive clip from Web Junkie above.