A new report published in Science seems to confirm something that many media critics have been trying to persuade us of for years — watching television makes us violent. This is the conclusion of a study by Jeffrey Johnson and colleagues at the New York State Psychiatric Institute, who showed that adolescents who watch television for more than one hour a day are significantly more likely to become violent than those who watch less.

Brad Bushman from the University of Iowa puts the problem into perspective: “The correlation between violent media and aggression is larger than the effect that wearing a condom has on decreasing the risk of HIV. It's larger than the correlation between exposure to lead and decreased IQ levels in kids. It's larger than the effects of exposure to asbestos. It's larger than the effect of secondhand smoke on cancer” (Washington Post, 29 March).

The study seems to indicate that the number of hours spent watching television, and not necessarily violent programme content, is the determining factor. However, as the Guardian (UK, 29 March) points out, “in the US, three to five violent acts occur in an average hour of prime time television, and 20 to 25 violent acts in an average hour of children's television”.

Johnson believes that his findings have profound implications. He says “By decreasing exposure to media violence, we may be able to prevent millions of Americans from being raped and murdered” (New York Times 29 March). Others, such as Steven Goodman from the Johns Hopkins University, were less convinced: "The question is, what makes kids different who watch TV for many hours as compared to those who watch little? You have to be extremely careful about making any causal inferences here” (New York Times).