Despondent children are easily overcome by chat room misery.
As one of Britain's foremost child psychotherapists, Julie Lynn Evans thought she had long since heard every parental nightmare. But last week, after reading the tragic story of 15-year-old Tallulah Wilson, who killed herself after visiting websites about self-harm and anorexia, she found herself in tears.
Her clients include three young people who have attempted suicide. What has become apparent to Lynn Evans during the sessions is that these desperate children have been tipped over the edge by things they have seen on the internet.
''When I read about poor Tallulah, the suicidal messages she left on Twitter, the history of using these chat rooms, it made me burst in to tears,'' she says. ''I am seeing this, day in day out. I thought as I was reading, 'It could have been any of the kids in my care, but for the grace of God.'''
She says the internet revolution is having a profound effect on children, taking many to a dark world that is doing them untold harm.
''It is the worst cohort of badly behaved kids I have seen in 25 years of work, and I'm absolutely convinced that the internet has a lot to do with it. It makes any problem more urgent, more dramatic.''
Teenagers haven't got anybody with a good, strong sense of self-worth to protect them when they are in there.
The parallels between Tallulah Wilson and the children Lynn Evans is treating are chilling.
On the face of it, the 15-year-old, described as ''clever, cheerful and creative'', who lived in a $1.5 million house and attended a $17,000-a-year private school in London, had every advantage. But since her death, it emerged that she was bullied and plagued by self-doubt. A message left on Twitter before she died read: ''I will never be beautiful and skinny.''
The case has led to calls for websites promoting anorexia and self-harm to be banned. Just four months ago, another schoolgirl, Rosie Whitaker, killed herself after visiting pro-anorexia sites.
Lynn Evans is on a mission to wake parents up to the dangers.
In her research for a book, she has entered the often-murky world of internet chat rooms to understand the messages that teenagers are exposed to for hours on end.
''The misery in those chat rooms is overwhelming and heart-rending - the sheer weight of it,'' she says. ''Teenagers haven't got anybody with a good, strong sense of self-worth to protect them when they are in there. The chat rooms become their reality.
''The anorexia ones are in some ways the most dangerous. Some of the images and conversations are terrifying. You are a success if your body mass index is 14, for instance - at that level your heart is being eaten up and you could die of a heart attack at any moment. Anorexia is the greatest cause of death of young girls. In these chat rooms, death is a triumph and they've got nobody to pull them back.''
''In a counselling session, I might get an agreement to compromise on certain types of dangerous behaviour, but then they go back to their chat room and the contributors say, 'she doesn't know what she is talking about,' and I lose my power in a second - as do the parents.''
In the case of self-harm, the internet seems to be fuelling an explosion.Britain's National Health Service published figures last year showing the extent of the problem. Hospital admissions for intentional self-harm have increased by nearly 10,000 - just over 10 per cent - in three years to 104,340.
''What the chat rooms are doing is teaching people how to do it and somehow making it OK,'' Lynn Evans says. ''Teenagers are telling each other how to hide the scabs, what medicine to use on them, how to avoid the marks. It creates the feeling that they are all in it together.
''It is everybody's kids. If it is not happening in your household - and if you have three kids, you will be lucky if you escape all of it - it will be happening to your friends. Wherever I go, I'm asked, 'What do I do?'
''I don't want to generalise - not all children are at risk and not all parents are unaware - but quite a lot of children are at risk and quite a lot of parents are unaware.''
While Lynn Evans supports moves to restrict access - including the proposal to require an ''opt-in'' to access hard-core porn and other sites - she believes responsibility lies with parents.
''It has to be an integral part of our parenting - like how children do their homework, what curfews they are set, and how they brush their teeth. It is not up to the government or the people making the software; it is up to us to be responsible.''
Part of that is knowing what your children are looking at on the web. Internet privacy for children is dangerous according to Lynn Evans.
She is generous in her praise of the positive aspects of the internet. But the longer-term impact of the internet is only just coming to light. ''This is so new and so huge. We just don't know what we are dealing with yet,'' she says.
''Teenagers have always been difficult and often unhappy, but it used to be private.''
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