"I was scared when the man's stomach was ripped open with a knife and the blood went everywhere," said an 11-year-old child in a Swedish study on the effects of television viewing on children.

Lund University sociologist Inga Sonesson headed a team that measured and monitored television viewing by 200 children aged 6 to 16 from the southern Swedish city of Malmo.Her book, entitled "Who Is Bringing up Our Children?" is to be published next month in Sweden. Its conclusions are shocking.

"We found a clear and unmistakable statistical correlation between excessive television and video viewing on the one hand and the development of anti-social behavior and emotional problems on the other," Sonesson told Reuters in an interview.

The researchers found that this held true even when home background was taken into account. Children whose parents were better educated experienced the same problems as those with less well-educated parents if the children watched a lot of television.

The study began in 1975 when Sonesson and colleagues first interviewed the children, who were selected to represent a cross-section of the population. The 6-year-olds were then at pre-school day-care centers. Subsequent interviews were conducted when the children were aged 7, 9, 11, 14 and 16 and the same young people are still being followed today.

At every stage, researchers also questioned teachers and parents.

Sonesson said she approached the project with positive feelings about television, which she believed could be an enjoyable and educational medium. But a different reality quickly emerged.

"I found that many 6-year-olds were seeing adult programs that were often violent and totally unsuitable. One very negative effect was that many were frightened. They had nightmares which followed them for a very long time," she said.

Children who at 6 were not described by their teachers as being aggressive, tended to become aggressive by the age of 12 if they watched several hours of television daily.

"What this shows is not that television viewing automatically leads to violent behavior. But, just as smoking increases the risk of cancer, television increases the chance of children having problems," Sonesson said.

Television viewing reached its height when the children were 11 to 12 years old. At that age, boys on average were watching 143 minutes a day and girls 123 minutes. But these averages disguised wide variations. Some children were watching far more.

Researchers asked the 11-year-olds if they had seen anything that disturbed them. These were some answers:

"A man placed a drill against another man's head and started drilling," said one child.

"I saw a pair of hands strangling someone," said another.

"She was chopped up alive," said a third.

One conclusion from the study was that there should be stricter controls on the most violent videos, backed by more stringent penalties for violators. But beyond that, a heavy burden rested on parents.

"Children should not just be stuck in front of the TV and left alone. We must explain things to them. Just as one teaches children how to cross the road, they should be taught good media behavior," Sonesson said.

"The dangers are not as apparent, perhaps, but they are real all the same."