His favourite titles were League of Legends and Honor of Kings, both owned by Tencent Holdings, the Chinese internet giant that is also behind the WeChat social messaging app.

“He had cut himself off from the real world,” said Li’s mother, Qiu Cuo, who cried while recounting the events of that afternoon. “We dared not block his access to the internet for fear he would harm himself. It was the end of my world.”

Li is one of about 100 mostly teenage boys and girls at the Adolescent Psychological Development Base, a drab collection of buildings located about 30 kilometres (19 miles) from central Beijing.

They are checked in, most of them against their will, by parents and guardians to undergo treatment for addiction to the internet, which was classified in China as a mental disorder in 2008.

Internet addiction has received fresh scrutiny after the World Health Organisation added gaming disorder to its international classification of diseases last year, 10 years after China first classified it as a public health threat.

China has stepped up its oversight of its video gaming industry following a directive by Chinese President Xi Jinping last August to the government to prevent widespread myopia among children.

Fewer new games were approved by the regulator and gaming companies were prodded to establish controls to limit the amount of time minors spend on gaming.

In the past year, Tencent, the market leader, has introduced age verification and limits on play time by young people. The Shenzhen-based company had no comment for this story.

In marked contrast, video game industry associations from the US, Canada, Australia, New Zealand, South Korea, South Africa and Brazil have resisted the WHO classification, calling on it to rethink the decision, which they charge “is not based on sufficiently robust evidence”.

Farewell my concubine: Chinese censors tighten rules for games

Under the WHO definition, gaming disorder is a pattern of behaviour characterised by impaired control over gaming, increasing priority given to gaming over other activities to the extent that it takes precedence over other interests and daily activities, and the continuation or escalation of the pattern despite negative consequences.

For a diagnosis to be made, the behaviour pattern must be sufficiently severe to affect important areas of functioning for at least 12 months.

Any decision to curb video gaming pits public health interests against the commercial interests of a lucrative industry.

In China, home to the world’s biggest internet population with more than 800 million users, the video gaming industry is estimated to be worth US$30 billion a year in revenue.

At the same time, playing video games is an increasingly popular pastime that is challenging other modes of entertainment for the attention and wallets of consumers.

The Post visited the treatment centre in Beijing earlier this month.

Run by Tao Ran, a former People’s Liberation Army colonel who headed army psychology units, the centre is one of the earliest places in China to diagnose and treat internet addiction and is said to have developed treatment protocols that are used in other parts of the country.

The facility consists of several buildings that serve as canteens, dormitories and treatment rooms, arranged around an internal open-air courtyard that doubles up as a basketball court and where patients assemble for exercise. No electronic devices are allowed.

Internet addiction is “such a big problem in China” and worsening with the popularity of smartphones, said Tao, who estimates that 10 per cent of China’s teenagers are obsessed with the internet.

“It’s no longer a problem for just teenagers. We have nine-year-old kids as well as 30-year-old adults. We’re also seeing more girls and children from rural areas.”

How to censor your internet, Chinese Communist Party style

Some are so hooked that they would wear adult diapers to avoid having to go to the toilet and interrupting their games, according to Tao.

One stole 30,000 yuan (US$4,345) from his parents, went into an internet gaming cafe in autumn and emerged the following spring.

Most try to escape and are “very defiant and arrogant” at the beginning, Tao said. “But results are apparent after months of treatment.”

Over the years, news reports of abuse at these detox treatment centres, including the use of controversial electroshock therapy, have prompted the government to increase its oversight of the industry.

Tao said that electroshock therapy and corporal punishment are not used at his centre, which charges about 10,000 yuan a month per patient and was set up in 2003.

Treatment consists of a combination of drug therapy, psychological counselling, physical exercise and family activities, and typically lasts at least three months.

Parents and guardians are required to stay at the centre, where they live in separate dormitories from their children and undergo lectures, such as those teaching them how to communicate with their children.

A typical day at the centre starts at 5am, where the patients are roused from sleep and gather for the first of several boot camp-style exercise periods at 6am.

China’s gaming freeze in 2018 hits small-time developers

After breakfast at 7.10am, it’s time for counselling sessions, more exercise and “other activities”, according to a schedule provided. The lights are switched off at 9.30pm. Weekends are devoted to cleaning, laundry, more exercise and a recap of the past week.

When we visited the centre at around 9.30am, the children were doing runs, push-ups and squats to barked commands from instructors wearing army fatigues. Many of them looked lethargic and reluctant.

Those who rebel are tied to their beds with restraints until they calm down, while more serious cases are kept alone in a small room for as long as 10 days, according to an account from one patient.

The centre confirmed the use of solitary confinement for “reflection, just like in the army”, but denied the use of restraints.

The dormitories are spartan and functional, with three double-decker bunk beds with thin mattresses and straw mats in each room. Personal belongings are kept in blue plastic containers with names written on them and shoes are arranged neatly in line.

For many of the children in the centre, it would be the first time that they are doing household chores and making their own beds.

Zhao Xiaojia, 15, remembers the day he was brought to the centre against his will.

An amazing video game that brings out the worst in human behaviour

“I shouted on the first day, I did not know where this place is and did not want to stay here,” he said. “I was not allowed to meet my parents, I clashed with the guards and was tied to a metal bed frame for half a day.”

Zhao had spent most of his waking hours on the internet for two months before his parents said enough was enough. He was on a QQ internet chat for three consecutive days and refused to take off his earphones even while asleep.

He goes for group therapy in the morning, where dozens of teenagers like him sit in a circle and discuss different topics with a psychiatrist, such as why they are depressed.

Then there are individual counselling sessions, activities with family as well as boot camp-style physical training.

Lunch at the centre is usually three dishes, rice and soup. “Noodles on Tuesday evening,” Zhao said. He has been at the centre for 280 days.

Wang Guoqiang, a factory worker from Hebei province, has stayed at the centre with his son for a year and has spent more than 150,000 yuan on treatment. It is a huge financial burden but worth it, he said.

Why Hong Kong schools should follow France's lead and ban mobile phones

“We are spending money to save the life of my kid,” he said. “He felt an emptiness in his heart and looked for fun in games.”

Just as his son undergoes counselling, Wang also takes classes to learn “how to be a good father”.

“I believe my son will adapt himself to society after getting out,” he said.