Research links TV viewing to aggression

Children who watch more than an hour of television every day are more likely to grow up into violent adults, according to a study that goes further than any other in proving the link between screen violence and aggressive behaviour.

The scientists behind the research, which involved analysing more than 700 individuals over a period of 17 years, believe that television viewing in childhood and early adolescence actually causes violent behaviour and that the link cannot be explained simply by the tendency of aggressive people to watch more TV. Neither, they say, can other environmental factors known to be associated with aggressive behaviour, such as poverty or bad parenting.

Jeffrey Johnson, of Columbia University and the New York State Psychiatric Institute, who led the research team, said the study, published today in the journal Science, should be seen as evidence for limiting the amount of television that young teenagers, in particular, are allowed to watch.

"Our findings suggest that, at least during early adolescence, responsible parents should avoid permitting their children to watch more than one hour of television a day," Dr Johnson said. "That's where the vast majority of the increase in risk occurs."

Between three and five aggressive acts are portrayed in a typical prime-time hour of television, but this rises to between 20 and 25 acts during an average hour of children's television, which includes cartoons, the researchers said.

The children in the study were interviewed with their mothers four times over the 17-year period, during which their ages ranged from five to 30. The scientists had access to criminal records as well as their subjects' personal recollections of aggressive behaviour.

Although there have been several previous studies of television viewing and antisocial behaviour, none has covered so many people over such a long period of time. Most of the earlier research looked at short-term increases in aggression and few of them followed youths for more than a year.

Dr Johnson found television-related aggression emerged most strongly in boys during adolescence, but in girls in early adulthood. The most common types of violence for boys were assault and fighting, whereas young women tended to commit robbery and make threats of injury. "It's quite surprising. We certainly wouldn't have predicted what we found," he said.

A major aim of the study was to resolve the "chicken and egg" question of whether television causes aggression or whether people who are more prone to aggression are more likely to watch more television.

On this question, the scientists looked at whether individuals with a history of aggressive behaviour were more likely to watch large amounts of television when they were a few years older. This was not the case, suggesting that heavy television viewing leads to aggression and not the other way around.

The scientists investigated other factors including childhood neglect, family income, neighbourhood violence, parental education and psychiatric disorders. Once these were taken into account, it was found that 5.7 per cent of adolescents who watched less than one hour of TV were violent to others in later years. In contrast, 22.5 per cent of those who watched between one and three hours a day committed aggressive acts later, as did 28.8 per cent of those who watched more than three hours a day.