IN MONTREAL, CANADA, a man walks into a school and shoots students randomly, wounding 20, one of them fatally, before turning a gun on himself. In south London, Britain, a four-year-old girl who can't read yells from the back seat of a car, 'Look mummy, there's McDonald's' because she recognises the logo. The incidents seem unrelated, but according to child experts both could be symptoms of a toxic phenomenon that is damaging children's brains: junk culture. Before Kimveer Gill, 25, went on the rampage in September he left a chilling comment in his online journal: 'Work sucks, school sucks, life sucks. Life is a video game; you've got to die sometime.' Fast food and small-screen addiction are hindering young children's brain development, according to a coalition 110 of Britain's leading education psychologists, child experts, children's authors and teachers. Aggressive marketing and even school testing regimes are squeezing the child out of them, pressurising them to act like mini- adults in a hyper-competitive world, with no regard for their emotional and social needs. This is 'almost certainly' a key factor in the rise of substance abuse, violence and self-harm among young people, the coalition says. An alarming rise in problems is being forced on children by the pace of social and cultural change, they say. 'We are deeply concerned at the escalating incidence of childhood depression and children's behavioural and developmental conditions,' they wrote in a letter to the Daily Telegraph. The letter, organised by Sue Palmer, a literacy expert, former headteacher and author of Toxic Childhood, and Richard House, senior lecturer at the Research Centre for Therapeutic Education at Roehampton University, has prompted a prolonged bout of soul searching. Its signatories include Baroness Susan Greenfield, director of the Royal Institution of Great Britain; Sir Richard Bowlby, president of the Centre for Child Mental Health; Professor Tim Brighouse, Commissioner for London Schools; Mick Brookes general secretary of the National Association of Headteachers; authors of books about children such as Philip Pullman and Aric Sigman; and three Children's Laureates: Anne Fine, Jacqueline Wilson and Michael Morpurgo. It has sparked a wide-ranging public debate about 'lost childhood' and a 'crisis of youth'. In her book, Palmer reports that childhood depression in Britain has increased by 50 per cent in the past 30 years and behavioural problems by 70 per cent. The prevalence of autism spectrum disorder has risen from 1:10,000 in the 1970s and 1980s to 1:166 by 2004, according to the American Academy of Pediatrics. A British Medical Association study in the summer reported that one in 10 children in Britain is being treated for mental health problems. Palmer said: 'There is evidence that children are emotionally less stable than they were and there are huge increases in child development disorders, such as attention deficit, dyslexia and dysphasia and autism.' The 110 experts suggest this is the result of children being starved of real play, real food and relationships with real adults, and have urged the British government to encourage an environment 'where kids eat healthily, play properly and develop vital life skills'. According to Dr House the problem is that important childhood experiences are being displaced by addiction to television, computer games, web chatrooms and texting. Yet children aged two to four are not remotely ready to spend their time on a mechanistic activity such as playing on a keyboard and it is doing them 'enormous harm'. 'If they start increasingly relating not with human beings but with machines, a crucial stage in their development is being missed and that is going to have long-term consequences,' he said. An advocate of Steiner education, he cites the Montreal shooting rampage - an alarmingly common phenomenon in North America - as a symptom of the alienation and cynicism that can take over young people in our technology-dominated world. 'Children need real play with real people. That is where they learn about social relationships, about managing their feelings of jealousy and envy and sadness and competition and all those things that children need to learn about relationships,' he said. The crux of his colleagues' argument is that junk food, lack of sleep and lack of play and exercise are linked not just to obesity but to brain degeneration. Keeping televisions and computers in the bedroom is a key part of that, because kids stay up watching and surfing when they should be sleeping, not just for their biological development but so they can learn, as during sleep the brain transfers what you have learned during the day into long-term memory. At the same time, sitting still in front of a screen displaces the time when they should be learning how to move, balance, deal with the risks of the real world such as hot and hard surfaces. And a diet of burgers and chips will deny them the fatty acids they need for their brain to grow. Palmer said: 'Some research published by King's College, London, earlier this year showed 11-year-olds, in terms of their commonsense conceptual understanding of the world, are two or three years behind where they were in 1990 because they are not standing outside making mud pies and dens or standing in streams, doing the things kids have always done. 'Before you can be literate you've got to have a basic level of language and movement. Before you take advantage of new technology you've got to develop the ability to focus your concentration at will, the ability to defer gratification and get along with other people.' She reacts angrily to media suggestions that she is a technophobic Luddite lost in a cloud of nostalgia or that she is shielding teachers by blaming parents for not controlling what children watch or eat. 'It's the whole culture feeding the children,' she said. With the proliferation of children's channels in the late 1980s and early 1990s, the TV moved into the bedroom - 80 per cent of children in Britain have a television or other electronic equipment in their room - and marketers began targeting children seriously. Children could give them guilt money, pester power and they wanted to nail down their brand loyalty from the earliest age. Governments have played their part, Palmer adds, by insisting on over testing pupils (standard tests every year in reading and maths from age eight to 13 for US children). They are changing the architecture of children's brains, making them 'pinched, miserable little creatures that can just pass tests'. Even the economic system is blamed for the long working hours and commuting time that starves children of quality time with their parents. 'You get the same reports in America, Japan, and Germany,' Palmer said. 'It is not necessarily global; it seems to be worse the richer the country is. It's as though the competitive drive of a really advanced consumer society has come between people: families split off into their own rooms to watch their televisions, whole communities have splintered.' Not everyone shares this nightmare vision. Robert Winston, emeritus professor of fertility studies at Imperial College London, describes the 110 experts' letter as an 'impressive fit of nostalgia'. He questions whether childhood depression is really on the increase - or merely being diagnosed more often - and suggested poverty and war were more likely causes than our materialistic, affluent society. TV, he said, had the power to educate and delight and while the average US teenager had seen 16,000 murders by their late teens, there was no adequate evidence of this causing much damage. The main area where modern children were seriously deprived, he said, was their lack of exposure to risk due to overprotective parents and public authorities. However, following the letter's publication, a number of research reports have been released seemingly supporting their views, several conferences have been organised to look into the issues and a parliamentary group is being launched by Baroness Greenfield, a member of the House of Lords and a professor of neuro-psychology at Oxford. It will include two former education secretaries - Estelle Morris and Gillian Shephard - and will look at the impact of modern technology on children's developing brains. So what simple advice would Dr House give parents anxious to ensure their children's brains grow to their potential? 'For the first seven years do not put your child in front of a television, computer or mobile phone,' he advised. 'Or at least ensure it is very strictly controlled.' Palmer offers three guiding rules: take the television, computers and mobile phones out of children's bedrooms; stop being overprotective, get together with other parents and help children play outside again by working for safer streets. Eat, shop, do hobbies and other activities communally as a family or as a group of family and friends. 'If you eat together you will be better able to control what they eat and fight the marketing messages,' she explained. 'But we should ban marketing to children under 12 - just take it away tomorrow.' Toxic Childhood: how the modern world is damaging our children and what we can do about it (published by Orion).