The news, when it comes, he seems to take well enough. A small sting of hurt behind the eyes, then a resigned attempt at a smile and a little shrug. Sinisa Savija leans over to exchange brief handshakes with his fellow contestants, before scrambling to his feet and turning briefly to make a stab at farewell. He manages only a game "Get on with supper!", before the show's host lays a kind but firm hand on his shoulder to lead him away, and he is gone.

Rarely can a small snatch of footage have been so closely studied for clues into the mind of a character on television, yet offer so little insight. Rewound time and again, studied frame by frame, there is nothing that could possibly hint at what was to come. It is a dignified reaction - one would hope to appear so composed having been told, with several cameras in your face, that you were a loser, a reject, the least popular person in the group. But by the time the Swedish viewing public got to see the footage, Savija was already two months dead, driven to a desperate suicide, according to his family, by that snatched, stinging moment of rejection.

It is almost exactly five years to the day since Savija left his home in Norrkoping in central Sweden for a nearby railway crossing, and stepped into the path of a speeding commuter train. The 34-year-old had returned only four weeks previously from the remote island in Malaysia where he had been competing in Expedition: Robinson, the Swedish version of the reality gameshow that was to appear some years later in the UK as Survivor.

Tonight, in the UK, the current run of Robinson's spiritual successor, Big Brother, comes to a close. It is a series that has provoked some of the most vicious vilification ever seen of normal people who happen to be appearing in a television show. Commentators and family members have expressed fears that the contestants, when they leave, may be at risk of violence or even suicide as a result of their treatment. Unless producers and press are reined in, the argument goes, something very terrible could happen. The sorry fact is, it already has.

Savija was the first contestant to be expelled from what was arguably the first-ever reality TV contest of its kind anywhere in the world - and according to those who knew him best, he took his life as a result. The bare facts alone, one might think, would be enough to give other broadcasters a moment to pause. Rather than frightening off other programme-makers, though, the experiment by Swedish state-funded broadcaster SVT in 1997 has been emphatically endorsed by other networks, which have scrambled to commission their own versions of this and similar formats. By last year, 40 different versions of Big Brother alone had been commissioned around the world.

But the story of Savija remains a nagging, cautionary tale - not least because successive participants in Big Brother and other shows have complained of depression, ruined reputations and trashed careers after taking part. Are we certain that reality TV programmes do not risk the mental health of their participants? And is it possible, before long, that we could see another tragic casualty?

The crucial question, and one that can never fully be answered, is the extent to which Expedition: Robinson contributed to Savija's death. As far as his wife Nermina is concerned, the programme is entirely to blame. "He became deeply depressed and agonised [after he was evicted]. He felt degraded as a person and didn't see any meaning in life," she said shortly after his death. "He was a glad and stable person before he went away, and when he came back he told me, 'They are going to cut away the good things I did and make me look like a fool, to show that I was the worst and that I was the one that had to go.' It is not a game when you choose ordinary people and put them under great pressure, constantly in front of the camera."

If the programme is to blame, however, there are few hints in the episode screened after Savija's death. His contribution, in fact, has been edited almost to invisibility. There is one particularly poignant moment where he is filmed sitting around a camp fire on his first night, exclaiming how excited he is. "It's a fantastic experience to be here. I'm not going to bed!" In fact, he was to last a mere four days on the island before being overwhelmingly voted off by his fellow contestants. He died on July 11 1997, nine weeks before the first edition of the pre-recorded show was broadcast.

The programme's producers, in their defence, hint at darker motives behind the suicide. "It's never been proved that this show was the reason it happened," says Gunilla Nilars, a senior producer in SVT's light entertainment department at the time, who went on to be executive producer of Robinson in 2000 and 2001. "If you asked a doctor, he would say he had problems already. He wasn't fit in his head, you could say."

Savija had lived in Sweden for only a few years when he volunteered for the show. Originally from a village in Bosnia, he and his wife had fled the former Yugoslavia during the worst years of the war. "Of course everyone was affected by the war," she told the Swedish newspaper Aftonbladet, "but Sinisa did not lose any loved ones. The reason for our coming here was that he was half-Croatian, half-Serbian, and I'm a Muslim. We didn't belong anywhere." Sinisa won a place at law school and they settled in Norrkoping, a small city 100 miles south-west of Stockholm. He loved sport, particularly basketball, and applied himself to learning Swedish.

In the spring of 1997, Savija decided to apply for a new programme being advertised by SVT. Eight men and eight women would be placed on a desert island, divided into two teams and left largely to fend for themselves, all the while competing with each other for a cash prize of 500,000 krona (£33,500). On his application form for the programme, he described himself as "peaceful, not subject to moods and very active". Friends said his selection for the competition made him as "happy as a child".

But if Savija applied for Robinson partly to affirm his sense of belonging, he was certainly unprepared for the very public rejection he would instead experience. Tore S Borjesson, a reporter at Aftonbladet, interviewed the contestants in depth before, and during, their time on the island. "I had a feeling when I met Sinisa that he was a bit shy, but he was certainly positive about it. I know he was active in sports, so he was a competitive guy. But what I remember clearly is that when I went out to the island after three days to interview the contestants again, he was the one who was suffering. It is very hard, he was saying, I can't take this. I think it was the whole thing - the physical conditions, and then the pressure to find his place in the group, and the risk of being voted off."

His less-than-fluent Swedish didn't help. "He didn't get on with so many people," says Martin Melin, the policeman from Stockholm who went on to win the series, and to become an overnight sensation in Sweden. "It's a social game, that's how it works. I think I won because I was friends with everyone, and I can get on with people from different social groups, different backgrounds. But Sinisa was a bit of a loner.

"It works the same way as it does in the country as a whole. If you are a refugee and you don't know the language and the culture - well, you're not in the group. You're different."

Despite Nermina Savija's accusations of bullying on the island, there is no detectable sense of menace in the tapes of the show to explain her husband's actions. (Indeed, after years of increasingly outrageous reality programming, the programme seems terribly tame and even a little dull, with rather more hugs and laughter than backbiting, and tasks that are almost amusingly innocent.) By the time the show transferred to the US, eagerly aped by CBS, executives were declaring definitively that Savija's suicide had stemmed from his experiences in the Bosnian war and a supposedly failing marriage.

Five years on, it is easy to forget quite how new and strange the format was of a reality gameshow, in which normal people would be filmed, in trying circumstances, trying simultaneously to form a community with, and compete against, a group of strangers, all the while periodically ganging up to isolate and reject the group's weakest member. For SVT, the programme, which at £2m was the most expensive they had ever filmed, was a huge risk.

"Nobody knew what to expect when we started filming it," says Nilars. "We had a brief on a page and some pictures. There was not even a pilot because it was too expensive."

The original idea, in fact, was British, the brainchild of Charlie Parsons, the co-founder of Planet 24 and the man behind the Big Breakfast. The concept had originally been developed for the US network ABC, but the untried format was deemed too risky. "A commercial station would never have started something like this, it was far too expensive," says Nilars. "They buy shows that they have seen are successful. But for us it was an experiment in a new way of programme-making."

But the reaction to the show, even long before Savija's suicide, was hostile. "The majority of the journalists writing about TV and the majority of newspaper columnists were very negative," says Borjesson. "They thought it was like organised bullying. Fascist television, one person called it. The host of the show said before it was filmed, to drum up publicity, that it would be like Lord of the Flies. He regretted it later, of course. There was no way he could have foreseen that there would be a suicide."

Once news broke of Savija's death, the chorus of complaints rose to a cacophony. Nermina Savija appealed publicly for the programme to be stopped, arguing that it broke broadcasting standards, but got nowhere. Ironically, says her lawyer PO Lefwerth, she didn't consider suing SVT, the one thing that might have frightened off the broadcasters once and for all. "I don't believe they had signed anything absolving the corporation of responsibility. She wanted to pursue it through the proper broadcasting channels. We're not that litigious in Sweden, or at least we weren't then." On September 13, the first episode, heavily re-edited, was broadcast - at which SVT immediately suspended it again. After a three-week break and a new producer, the series recommenced. SVT's head of entertainment resigned shortly afterwards.

But then, inevitably, something strange began to happen. The audience, relatively small at first, steadily began to build. "In order to take part in a conversation, at work, when you had a coffee, wherever, it was all Robinson, Robinson, Robinson," says Borjesson. Half the viewing population of Sweden tuned in to see the series conclude on December 13. Borjesson estimates that for the next two years he spent 80% of his time writing about nothing but Robinson. And Savija? "I think people had already forgotten about it, because they found they liked the series."

He might have been quietly airbrushed out of the story of reality TV, but lessons have undoubtedly been learned from Savija's death. Most broadcasters argue that their psychological screening is much more rigorous than in the past. The contestants for that first show included not only a recent refugee from a war, but also a man who admitted he applied partly to prove to himself he had recovered from a childhood rape, and another man who had been jailed for drug smuggling.

Ironically, those arguing in favour of continued reality programming suggest that their best defence against another tragedy such as Savija's is the very fact that the genre has become so ubiquitous. Savija had no idea what to expect, the argument goes, and so came to imagine the worst about how he would be portrayed and what it would mean for his life.

But it is manifestly wrong to suggest that having seen it all before on TV prepares normal people for the potentially devastating psychological effect of appearing on a show of this type. The principal complaint of almost every former contestant on Big Brother is that they did not get enough psychological support after leaving the programme. Nermina Savija's argument, articulated passionately in the weeks after her husband's death, was a simple one: is it not simply absurd to suggest that a television programme that requires intense psychological screening beforehand, and the offer of careful psychological help afterwards, does not risk contestants' mental health?

In August 2000, Philip Harding, the BBC's director of editorial policy and most senior arbiter on ethical standards, warned that the very high levels of stress experienced by participants in reality contests might one day lead to a death. He was almost certainly unaware that he was three years too late.