The condition is particularly common in Asian countries including South Korea, but China appears among the hardest hit because of its huge number of Internet users, Greenfield said.

"China is leading in showing how bad this could get," he said. "Because of the sheer amount of numbers, they're sort of showing worst-case scenarios."

Among Chinese youth online, nearly one in 10 is addicted to the Internet, according to a government-sanctioned report published this year. Most of those youth also suffer from poor relations with their parents, peers and teachers, according to the report.

About one-third of China's 300 million Internet users were under 20 years old at the end of last year, according to the China Internet Network Information Center.

Internet addiction has not been formally labeled a pathology in either China or the U.S. But Greenfield argues that there is growing consensus and expects some kind of recognition in the U.S. in the next two years.

Estimates of Internet addiction rates in the U.S. run from about 3 percent to 8 percent of the population, Greenfield said.

Symptoms include an inability to cut down on Internet use and a negative physical or emotional reaction to having access removed, such as how a drug or alcohol abuser would feel if blocked from the substances, he said.

Among the other centers for Internet addiction in China is one that stirred controversy in recent months for its use of electric shock treatment. The center in eastern Shandong province has halted the treatment since it drew widespread media attention, a woman at the center surnamed Yang said by phone. At the height of the controversy, anonymous bloggers wrote about receiving the treatment and hackers defaced the center's Web site, which has since remained offline.

The shocks were meant to make patients associate a negative feeling with Internet use, according to the center. Yang declined to comment further on the treatment.

China's health ministry may soon ban shock treatment for Internet addiction, according to Tao. A health ministry spokesman said officials were researching the treatment to determine its legality.

Tao, who holds a master's degree in medicine, designed the treatment program for his own center with a group of other doctors, he said, sitting beside a small portrait of Sigmund Freud in a treatment room. The team drew on their academic studies and on foreign programs including Alcoholics Anonymous, which inspired a schedule of mutual check-ins and support that Tao sets up for families who have completed the program, he said.