Blow for teens' TV time

Teenagers who watch more than one hour of television a day are more likely to become violent adults, say US researchers. The large-scale, long-term study is one the first to show such effects on adolescents and young adults1.

Current advice on TV viewing, such as the American Academy of Pediatrics' recommendation of 1-2 hours per day, might set the bar too high, says Jeffrey Johnson of Columbia University in New York, a member of the research team.

"If parents want to minimize the risk that their children grow up to commit aggressive acts, they should attempt to limit their viewing to less than one hour per day, on average," he says.

Many psychologists regard the link between media violence and violent behaviour as well established. Other researchers see it as unproven, and say that the new study is flawed.

On the box

Johnson and his colleagues have been following 707 families in upstate New York since 1975. They used statistics to separate TV viewing from other factors contributing to aggressive behaviour, such as family income, education and prior history of violence. The team hopes it has split the possibility that television causes aggression from the possibility that aggressive people watch lots of television.

The biggest jump in aggressive behaviour occurred between adolescents who watched less than one hour of TV per day and those who watched 1-3 hours, all other things being equal, the researchers found.

The trend towards violence continued with increased viewing. Children who watched three or more hours of TV per day between the ages of 14 and 16 were roughly five times more likely to commit violent acts as adults than those who watched less than one hour.

The new study shows that youths are vulnerable to the effects of media violence over a broad age range, says psychologist Craig Anderson of Iowa State University in Ames. "We can't sit back and say that after 12 it no longer matters."

"People may be particularly sensitive to the effects of media violence in early adolescence," says Johnson. "It's a critical period of life for the development of social skills and personalities."

Spoiling the view

But other psychologists criticize the study's methods. The way that Johnson's team divided people by their viewing habits invalidates their results, says Guy Cumberbatch, who heads the Communications Research Group, a UK company that does broadcasting and social-policy research.

Only 88 adolescents averaged less than one hour in front of the box each day, he points out. This group is "so small, it's aberrant", he says - its members will probably have many other characteristics not reported in this study, such as being teachers' offspring or devoutly religious.

It would have been better to split children into high, medium and low viewing groups, rather than force them into categories, Cumberbatch believes. Johnson's team has "tortured the data till they confess", he goes on, calling the group's conclusions "a remarkable feat of topsy-turvy logic". Johnson counters that dividing TV viewers into the groups that Cumberbatch suggests would not have affected the study's basic results.

The link between television and violent behaviour is still far from clear, believes Helena Hird, spokesperson for the Independent Television Commission that regulates commercial television in Britain. "There's plenty of research that shows quite the contrary," she says.

For example the Atlantic island of St Helena only got television a few years ago. Children there have not become more aggressive, possibly because they live in close-knit, carefully supervised communities.

References

1. Johnson, J.G. et al. Television viewing and aggressive behavior during adolescence and adulthood. Science, 295, 2468 - 2471, (2002).