After the apparent suicide of a teenage contestant, Dr Raj Persaud says it's time for TV to stop exploiting vulnerable people

Carina Stephenson was delighted when her family was selected to spend four months in the Australian bush, living the tough lives of early settlers for a six-part History Channel series called The Colony. The filming went well and Carina, 17, is said to have been "happy and positive" after the experience.

Last Saturday, Carina was found dead in woods near her Yorkshire home. This terrible tragedy must raise the question of whether her participation in reality TV may have contributed to her apparent suicide.

Carina's parents previously revealed that she had told her family that she was a lesbian, and had been spending a lot of time in internet chat-rooms. This would naturally raise the question of whether, as an adolescent, Carina had been going through a period of emotional turmoil. If so, this may not have been an appropriate moment to expose her to a reality TV show.

This is not the only recent case of a personal tragedy which may be linked to this controversial broadcast genre.

On 11 July 1997, Sinisa Savija, from central Sweden, hurled himself into the path of a train. A month earlier, the 34-year-old had returned from a Malaysian island where he had been a contestant in the reality TV show Expedition: Robinson. Savija was the first contestant to be voted off the island. According to his widow, it was not a decision he took well and the prospect of his stinging rejection being broadcast across the country was enough to send Savija over the edge.

On 14 February this year Najai "Nitro" Turpin, a 23-year-old boxer, shot himselfa few weeks before broadcasting was due to start of a boxing reality show called The Contender - for which his filming had already occurred.

In March a television producer, Melanie Bell, leaped to her death from the top of the Stratosphere Hotel in Las Vegas. She was taking part in Vegas Elvis, an "experimental reality show that features the film crew as part of the featured cast".

The production company issued a press release in which it pointed out that the show "became the second reality program in less than two months to suffer a cast member suicide" and that "unlike Najai Turpin of The Contender, Bell's family and friends knew she suffered from severe depression which stemmed from her battle with Anorexia".

The release also said that "[s]he was recently released from an undisclosed eating disorder clinic in Alabama, where she had successfully gained almost 40 pounds in less than six months".

TV companies claim to screen contestants for the kind of emotional dysfunction that would render them damaged by their experience on camera. Yet they have persistently refused to divulge the precise details of this screening, or the kind of assistance offered to participants during the programme or after it is over. The programmes are also purposefully vague about the qualifications and credentials of the therapists they use.

In the unregulated world of psychotherapy, anyone can call themselves a psychotherapist without facing any legal sanction The only terms in this confusing area with anything close to legal standing are "psychologist" and "psychiatrist". While adding legitimacy to the genre, no psychologist or psychiatrist would be allowed to veto the use of a contestant.

Endemol, which produces Big Brother, also made a recent series called Shattered, a reality show where there was a prize for the contestant who could, over several days, do without the most sleep.

The programme attracted trenchant criticism from Neil Douglas, professor of respiratory and sleep medicine at Edinburgh University and president elect of the Royal College of Physicians of Edinburgh, and Professor Jim Horne, director of the Sleep Research Centre at Loughborough University. Dr Trish McNair, a member of the ethics panel advising the show, said the panel's recommended ban on electric shocks had been ignored.

Producers will want to deploy characters whose weaknesses, foibles and disfunctions render them likely to respond with watchable stress or conflict to scenarios the TV company concocts. Serious mental health professionals are likely to select contestants who are so stable that watching them calmly resist the provocations around them would be like watching paint dry.

Reality TV companies do not make it clear which category of therapists they are referring to when trying to defend their credentials.

There are three distinct groups involved and often there is no overlap between them. First there are the "talking heads" on camera, commenting on contestants' behaviour. These are often the most properly qualified. Then there are the therapists doing the screening to decide who is fit to take part. This group is often different to the therapists working behind the scenes once the programme has started.

I have spoken to many contestants. The screening is usually at the level of sophistication of questions such as "what is your favourite film"?

The defence will inevitably fall back to the contention that participants are not forced to take part. Yet Cynthia McVey, of Glasgow Caledonian University who was a consultant for the BBC's Castaway series, does not believe informed consent is possible.

She points out that a new twist in the genre is to spring surprises, often of an emotionally disturbing nature, and cites as an example a recent series of Big Brother in which the producers turned the "house" into a boot camp. Two housemates were given the status of "sergeants", with authority over the others, the "privates". The sergeants had to oversee a series of tasks. Unknown to the privates, the prize for completing the tasks was immunity from ejection. For the sergeants.

When this deception was revealed, it caused considerable trouble. Two housemates engaged in a screaming match, insults were thrown and one threw a shoe at another and then broke down in tears.

The producers of Big Brother say all housemates go through a psychological assessment by an independent chartered psychologist with post graduate degrees in clinical psychology and psychotherapy. "In addition," says a Big Brother spokesman, "enquiries are also made about their medical history, recent prescriptions and illnesses. All the housemates are deemed fit, well and psychologically robust enough to cope with the intense environment of this game show."

There is also "24-hour monitoring and on-site psychological and aftercare support". And Big Brother housemates are free to leave the show at any time.

But for psychologists, the Big Brother boot camp was reminiscent of an infamous experiment carried out in California in 1971 by Philip Zimbardo of Stanford University.

Zimbardo's constructed a "capsule environment" not dissimilar to the Big Brother house, in which one group of students were told they were prisoners, others that they were guards. Within hours the guards began bullying and humiliating the prisoners and Zimbardo was forced to halt the research. The experiment seemed to have got out of control so quickly due to the powerful psychological processes unleashed.

There are significant similarities between the Stanford Prison Experiment and shows like Big Brother. Both situate participants in conflict and compel them to make decisions in taxing and strange situations, while cutting off their normal social support network.

What the field learned over 30 years ago, which impelled mental health professionals to stop the experiment before it went too far, has yet to be learned by television.

We must ask how many more tragedies it will take before someone at last intervenes to stop this out-of-control "experiment"?

Raj Persaud is a consultant psychiatrist at the Bethlem Royal and Maudsley hospitals, and Gresham Professor for public understanding of psychiatry

Who shouldn't have their 15 minutes

The following personality types are unsuitable for reality TV, according to Cynthia McVey, a psychologist at Glasgow Caledonian University and consultant on Castaway.

* Needy people. People who crave acceptance often equate the attention of the nation with the love they want. When stressed or drunk such people embarrass themselves, undermining their very motivation for appearing on TV.

* Seriously ill people. People who have a serious psychiatric illness such as schizophrenia should never participate, in case of a schizophrenic attack.

* Anxious personalities. Analysis by psychiatrists or psychologists should veto people with even slight anxiety or depression. These people can be very emotionally vulnerable, and it is vital that the analysts have the last word on who should go on the shows.

* Less intelligent people. Some people without psychological problems can find themselves in difficult and damaging situations if they are less intelligent than the other people in a group.

Alice Fordham