When Brent Runyon was 14, he soaked his favourite black bathrobe in petrol, slipped it over his shoulders, and struck a match. When nothing happened, he held the flame closer to his body. At which moment his life, and the lives of his family, changed beyond recognition. In the seconds that followed, the flames burned through 85 per cent of Brent Runyon’s skin, condemning him to months of indescribable pain and a lifetime of disfigurement. Fourteen years later, he is still coming to terms with what he did to himself and to those around him, and still battling with the depression that had made him want to end his life at such an early age, and in such an appalling manner.

By his own account, Brent Runyon entered adolescence with everything going for him. He lived with his teacher mother, college administrator father and brother Craig in a comfortable suburban home in Washington DC. They enjoyed family holidays and trips to museums, and Brent was a good-looking, popular boy who did exceptionally well at school. But he begged to be taken out of a special programme for gifted and talented children. “None of the cool kids were in it,” he wrote later in his book, The Burn Journals, published this month. “Well, one, if you count me.”

In retrospect, says Brent Runyon, his return to the regular classroom marked a turning point in his life. Always a “straight A” pupil, he now began getting Fs, and was more than once suspended from school. He had taken to wearing black, and seemed to enjoy peppering his conversation with references to death. And then came the incident in the locker room. It was a silly thing; a bit of messing about that went wrong. He grabbed a book of matches from another boy and set it alight; when it flared up, he panicked and tossed it into a locker, damaging a shirt. The next day, the school launched an investigation into the “arson” incident and Brent Runyon became convinced he was about to be expelled. It was enough to drive him over the edge.

For some time, he had been making half-hearted attempts at suicide: taking pills, cutting his wrists and experimenting with ropes. It was part of some inner darkness that seems to have descended on him around the age of 13, and although his family remained unaware of what he was going through, he would tell his closest friends all about it, building his suicide attempts into his crazy-but-cool persona. And so when a classmate, on hearing of his involvement in the locker-room incident, asked him what he was going to do, she was not surprised by his reply: “I’m going to set myself on fire.”

Years later, his radio producer girlfriend, Christina Egloff, urged him to tell the story of his ordeal and subsequent recovery, and helped him to shape his notes into a book. When The Burn Journals was published in the United States last year, it immediately struck a chord with teenagers who identified with the young and troubled narrator. Brent Runyon began giving talks about his experiences, and was soon being invited to schools all over the country to talk about depression and the ever-rising tide of teenage suicides.

His manner is self-effacing - “stupid” is the only printable word he uses to describe what he did at 14 - and he is quick to point out that he offers no easy answers for parents and teachers, and no simple tick-box guides to identifying those most at risk. “The first thing you think of is those kids who wear all black - like those Columbine kids wore all black (in 1999 two students shot dead 12 fellow pupils and a teacher at Columbine high school, Colorado), and I wore all black,” he says. “But unfortunately, it’s not that simple.

“It would be great if everybody who bought a Morrissey record was tagged and you could follow them around like wild animals. But in some cases the one who is really hurting might be the son of the football player - the boy with the pretty girlfriend driving the fancy car.

“In my town, a kid like that killed himself last year, and he was only 12.

He was popular and he was athletic, and that’s how the papers would have described me if I’d died.”

Brent Runyon does believe, however, that while children might not tell their parents or teachers how they feel, they generally share their anxieties with friends, and tapping into this knowledge might save lives.

“Kids of course know who’s going through these things. But there’s this code of silence. You don’t want to be the rat who turns your friend in. So why not have an anonymous way to communicate between adults and kids? Would it be so difficult to have a box in the middle of the school where you just stick a name in?”

Such communication between age groups, he says, needs to be two-way, and adults must be prepared to share their own adolescent experiences with children, even if doing so exposes them as vulnerable and less than perfect. “Adults think they have got to set a good example and they don’t want to give kids ideas. But empathy to me is one of the key emotions that’s overlooked. Nobody is honest about the way it feels to be a teenager.” Having apparently forgotten their own experiences, adults are too ready to dismiss their children’s emotional ups and downs, he says.

“There’s this preconceived idea that all teenagers are moody bastards and you just have to wait until they’re 19 and they’ll be fine. But then a teenager will do something terrible to themselves, and it’s like, why didn’t anyone do anything?”

Brent Runyon would like to see a deeper understanding of mental illness generally, and a greater awareness of the symptoms of incipient depression in particular. For his own part, he says, writing the book has given him a valuable insight into what happened to him, and how he is still affected by the cycle of depression. “When it came out, and people were coming up to me at book signings and saying they had been depressed too, I started to recognise in my mind the same kinds of thoughts that were in there when I was a teenager. Like driving down the street and seeing a telegraph pole and, for a split second, wanting to wrap my car around it.

“It’s a case of keeping in touch with what the brain is doing, because it can get out of control. Last October, a month after the book came out, I started having therapy again for the first time in nine years, and that has helped me recognise what my patterns are. It’s scary to admit that this guy who set himself on fire was thinking about driving his car into a tree. But just asking for help seemed to immediately lift about 200 tons off my shoulders.”

Runyon is now working on a novel “about teenagers, life and love”, a combination of subjects that he admits to finding endlessly fascinating.

“It’s the first time that teenagers are feeling these things,” he says, “and it’s huge. That’s why they are such great foils for drama. Look at Romeo and Juliet. Crazy teenagers fall in love and end up killing themselves!”

Not surprisingly, perhaps, there is a darker side to his fascination. “The way that kids internalise the pressures of the world and then make their pain external is so disturbing that I can’t even think about it,” he says.

“I live my life pretending that it doesn’t really exist, because it’s so awful. I like to pretend that it all stopped as soon as I lit that match - that everyone else was fine after that, and that no one else is in as much trouble as I ever was. But that’s just me, defending myself against the pain of the world.”

The Burn Journals is published by Penguin, pound;12.99