When Johnny’s* grandmother died unexpectedly, the family was devastated. Fifteen-year-old Johnny seemed to be coping well, but would continue to spend at least six hours a day playing online role-play game World of Warcraft; sometimes up to 10 hours at the weekend.

It was not until months later, after he had cut down on his gaming, that the impact of the death really hit home. Johnny went to visit his grandfather and was horrified to relearn that his grandmother had gone and would not be coming back.

“He did acknowledge it, but was so immersed in World of Warcraft at the time that when he got off the game, he was shocked and very upset that she wasn’t there,” says Dr Richard Graham, a consultant child and adolescent psychiatrist who subsequently treated Johnny for his gaming addiction.

The time Johnny spent gaming had steadily increased over the years until he was spending every available hour on his Xbox. He completely lost all interest in school and his grades inevitably suffered. It was only after a couple of months of treatment that Johnny started to re-engage with the people around him. “That emotional impact had been frozen in time,” says Dr Graham. “Even when there was a death in the family, something as crucial as mourning didn’t take place.”

Johnny was one of the first patients to benefit from the rehab service for young technology addicts at the private Capio Nightingale Hospital in London, which opened earlier this year. The residential unit is the first of its kind in the UK to treat teenagers whose reliance on technology has got out of hand.

Children have access to more technology now than ever before. Few teenagers do not have a mobile phone and the use of a home computer, as well as a games console, such as an Xbox or PlayStation. This technology is much more than a peripheral tool: from texting friends to using social networking sites such as MySpace, Facebook and YouTube, it has become embedded in many children’ lives.

But there are signs that for some their use of technology is turning into an addiction. A 2009 study by Cranfield University in Bedfordshire found that more than 60 per cent of teenagers admitted to being “quite” or “very” addicted to the internet, and more than half said they were addicted to their mobile phones. The respondents spent an average of one to two hours a day on social networking sites.

Research published in April this year by the Pew Internet and American Life Project, the world’s largest data provider on the impact of technology, found that 50 per cent of US teenagers send 50 or more text messages a day - 1,500 a month. Around a third send more than 3,000 texts a month. While 75 per cent of teenagers in the study owned a mobile phone, 80 per cent of 12 to 17-year-olds had a games console and 73 per cent used social networking sites.

These technological habits are having an impact on schools. Fiona Hammans, headteacher of Banbury School, Oxfordshire, says she has been approached by two sets of parents who were concerned about their sons’ gaming habits.

“One of the pupils was in Year 11, and his mum said he was spending all his time gaming online rather than doing revision, often staying up until three in the morning,” says Dr Hammans. The boy’s mother felt that his grades were slipping as a result, but he became very aggressive when she tried to limit his internet use.

But approaches from parents can put teachers in a difficult position. When use of technology directly affects relationships in school, such as when offensive messages are posted on Facebook, teachers can be justified in stepping in. But Dr Hammans draws the line at dictating how much time children should spend on computer games at home.

“It’s really difficult,” she says. “How can a teacher give advice on what goes on in the home? I’m not going to do that - it’s interference.”

The school can encourage pupils to use technology wisely, however. At Banbury, the ICT curriculum includes lessons on the impact of an individual’s actions on social networking sites, as well as how to be safe online.

Gillian Low, headteacher of the Lady Eleanor Holles School, Middlesex, believes teachers have an important role to play in making sure young people do not become too dependent on technology. But she is also realistic about what schools can achieve.

“We can’t try to stop the tide,” says Mrs Low, who is also president of the Girls’ Schools Association. “Technology is here to stay.”

Dr Graham established the addiction service at the Capio Nightingale after seeing the effect that increased use of technology was having on his young patients. “We know adolescents are very much influenced by the context and the world that they live in,” he says. “With the rise of social media and constant messaging, different problems were arising that seemed to affect both sexes: body image problems, eating disorders or self-harm following cyber bullying.”

Sixteen-year-old Jamie* spends 70 hours a week on his computer, including two 12-hour sessions on a Saturday and Sunday. Most of this time is spent in chatrooms discussing Star Trek and other sci-fi shows.

Jamie admits that the internet is the most important thing in his life. “I log on until I am physically unplugged by someone else,” he says. “I can’t work or live without it - my social and intellectual lives are linked directly to it.”

His internet use means that the household bills are huge. The teenager’s solution to this is to stay up all night when the tariff is lower, even if it means he sleeps in and misses school.

Psychologist Mark Griffiths, an addiction expert from Nottingham Trent University who worked with Jamie, says characteristic behaviour of a young addict includes withdrawal symptoms, conflict with parents, increased tolerance levels so that the young person needs to spend ever-increasing amounts of time on their activity, and extreme mood swings.

But some health professionals can shy away from labelling such behaviour as addiction. Dr Griffiths distinguishes between addictions where the internet is used as a means to an end, and addictions to the internet itself. “If gambling addicts can’t gamble on the internet, they will gamble at the bookies or a casino,” he says. Internet addicts are hooked on activities they can only do online, such as social networking or role- playing in chatrooms, he adds.

At its extreme end, technology addiction can have tragic consequences. In May, a married couple in South Korea were convicted of negligent homicide after leaving their three-month old baby to die while they spent the majority of their time role-playing in a virtual reality game.

Most teenagers treated at the Capio Nightingale have been referred by parents who are unable to cope with their child’s aggression at the prospect of having their use of technology curtailed, or concerned that their child’s behaviour is affecting their schoolwork or social skills.

Initially, inpatients have to go “cold turkey” and live without any of the technological devices they are used to. With its soft furnishings and soothing surroundings, the hospital’s calming atmosphere is intended to comfort and support addicts before they go back to the outside world.

The treatment involves exploring the history of their technology use and how it became problematic. Rather than aiming to cut them off from the source of their addiction altogether - technology is such a crucial part of day-to-day life - it is intended to help patients acknowledge their problems and develop healthy habits. Therapy also looks at the patient’s relationships with family and friends as well as other aspects of lifestyle, such as nutrition. Dr Graham recounts the case of one 16-year- old who became severely underweight after gaming took priority over eating or exercising.

Studies have shown that extensive internet use can create a dependency. Research into the habits of 1,000 teenagers in Australia and China, published in the Archives of Pediatrics and Adolescent Medicine in August this year, found that just over 6 per cent were pathological users: they felt depressed, moody or nervous when they were not online. This group was also two-and-a-half times more likely to be depressed than their non- dependent peers.

Some teenagers find it easier to form relationships online. Jamie, who is happy to spend all his time discussing Star Trek, has been able to find like-minded people online. “The internet can perform a socially useful function,” says Dr Griffiths. It is difficult to say whether it is poor social skills that lead people to excessive internet use, or whether excessive internet use leads to poor social skills, he adds.

Dr Graham says that technology addicts do not conform to a single stereotype. “The idea that we would see socially awkward, shy people is not the whole story,” he says.

Many teenagers spend the majority of their time online interacting with other people. But addiction or extreme use of these media can make it difficult for them to communicate face to face in a meaningful way. “These people do want relationships,” says Dr Graham, “but they take advantage of technology to cut out some of the more difficult aspects of dealing with people. With Twitter, for example, you can’t actually say that much. It trims some of the more awkward moments that you might have in conversations.”

For teenagers, who are at a crucial time in their social development, this can have huge consequences, argues Sherry Turkle, professor at the Massachusetts Institute of Technology and author of Alone Together: Why we expect more from technology and less from each other.

“The real demands of friendship, of intimacy, are complicated. They are hard and they involve a lot of negotiation,” she says. “They are all the things that are difficult about adolescence. And adolescence is the time when people are using technology to skip and to cut corners and not have to do some of these very hard things.”

The opportunity for 24-hour communication raises additional problems. “There is an anxiety of disconnection; that these teens have a kind of panic,” says Ms Turkle. “They say things like: `I lost my iPhone; it felt like somebody died, as though I’d lost my mind’.”

One of Dr Graham’s patients refused to leave the computer and go to bed for fear that she would miss out. For this 13-year-old, there was, in effect, a massive social gathering going on with up to 100 friends online at the same time, he says. “A fundamental fear of being excluded is very dominant.”

Marie*, 17, updates her Facebook profile four times a day on average. She is studying for her A-levels, but would go online for three or four hours when she got in at 5pm, “then I still have to do all my homework that night,” she says.

She is under no illusions about the effect this is having on her schoolwork. “It is definitely a distraction,” she says. “If I go online to do research, I would always go on Facebook first and then I end up spending loads of time checking what everyone has been doing.”

She laughs when talking about the amount of time she spends online. “I know I am quite extreme,” she says. “I’m never really not online. I would usually be watching American TV on my laptop and chatting to my friends on my iPod Touch or texting them on my phone. You can be online even when you are in town now, so I’m always checking Facebook.”

Identical twins Michael and James, 15, spend around five hours a day gaming. Their mother Joanne persuaded them to go to a family therapy session at the Priory clinic, but the twins do not accept that they have a problem.

“Personally, I don’t think I’m addicted,” says Michael. “If I am addicted, then I am just as much as anyone else. I’m no worse than my friends at school, as we play at the same time.”

He takes part in a lot of sport at school, but also loves playing video games - Call of Duty and Gears of War are the current favourites - usually with his brother and four or five friends. He spent a month away from the Xbox while on holiday but took a handheld Nintendo with him, “just to play if we don’t have anything to do”.

The boys’ mother became worried when their school marks began to fall. “Being so busy with life, you don’t always have 100 per cent control over what they’re doing,” says Joanne. “It just gets to a point where you try to control it, but whenever it’s available that is all they want to do.” She and her husband decided to get outside help when they realised their sons were not listening to them.

For Joanne, it is the impact on their social skills that worries her most. “They are convinced that they are socialising with their friends, as they can speak with them on headsets,” she says. “But my husband and I both know they’re not socialising: you need to be speaking to someone face to face and looking them in the eye for that.”

Her attitude may reflect a view of socialising that is not shared by today’s teenagers, but many parents have similar concerns. This generation gap can also blur the line over how much technology use is too much.

For Simon Widdowson, an ICT co-ordinator at Porchester Junior School in Nottingham, pupils’ enthusiasm for technology is an asset to their school work. “If I pair pupils up for work on laptops they work much better than if they were working on their own,” he says.

When technology is used in lessons there is a marked improvement in concentration and behaviour, he says, although it is hard to tell whether that is because pupils do not want to miss out on using the laptops or because they simply prefer working that way.

“It does seem sometimes as though working using technology results in them being more proud of their work than when they are not using it,” he adds.

As well as his work at the Capio Nightingale, where he has had consultations with 50 parents concerned about their children’s internet use, Dr Graham also treats teenagers on the NHS for problems compounded by their technology addiction. He argues that we need to change our attitude towards technology.

“We as a society need to work towards better tech hygiene,” he says. “I’m really starting to think that we should try to go for three days without technology, for example. It’s very difficult to know what life would be like without it.”

But while technology does cause serious problems for young people, the medical profession in the UK is still in the process of defining the terms of technology addiction and how problems should be addressed. “I don’t for one minute believe we should demonise the internet,” says Dr Griffiths. “For most of these people who have problems, they would probably have problems elsewhere in their lives. What the internet does is enhance that predisposition they already have.”

For Marie, an awareness of the impact her technology use is having on her life has led her to impose her own restrictions. She now studies in a library that bans Facebook access before 5pm and tries to stay aware of her dependence. But she has no intention of cutting technology out of her life altogether. “If it got to the point where I was sitting at home on my computer and I wanted to stay online rather than go out with my friends,” she says, “that’s when I would start to think it was a problem.”

Names have been changed.

• Original headline: Screen burn