Watching more than one hour of television per day may make adolescents more prone to violence in adulthood, according to new research. The study in the journal Science is the first to investigate the long-term effects of television viewing on aggressive behavior during adolescence and adulthood, the authors say.

Jeffrey Johnson, of the New York State Psychiatric Institute and Columbia University, and his co-authors tracked more than 700 children from adolescence to adulthood.
They found that adolescents who watched one hour or more of television per day were more likely in their late teens and early twenties to engage in aggressive acts against other people. This was especially true for boys.

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

Young adults--especially women--who watched two or more hours of television per day were also more prone to violence.

The link between watching television and violence remained intact after the researchers had accounted for other factors that might be responsible for television viewing and violent behavior, such as childhood neglect, low family income, or a psychiatric disorder during adolescence.

The youths in the study and their mothers were interviewed four times over the course of 18 years and assigned to three categories: those who watched less than one hour of television per day, between one and three hours per day, and more than three hours per day.

Johnson and his colleagues reasoned that television watching in general would reflect the amount of televised violence seen. Three to five violent acts occur in an average hour of prime-time television, and 20 to 25 violent acts occur in an average hour of children’s television, according to the authors.

Information on aggressive acts committed by the study subjects came from interviews of parents and their offspring, as well as state and federal records of arrests and charges for adult criminal behavior. The researchers grouped the violent acts according to whether they occurred around age 16, age 22, or age 30.
 

The study thus contradicts a common assumption that media violence affects only children, say Craig Anderson and Brad Bushman, of Iowa State University of Science and Technology, in a related commentary.

An unexpected gender difference emerged as the study went on, with the link between aggression and television watching being strongest for males during adolescence, and for females, during early adulthood. While the most common types of violent behavior for boys were assault and fighting that led to injury, violent behavior by young women also included robbery and threats to injure someone.

“It’s quite surprising. We certainly wouldn’t have predicted what we found,” Johnson said.

Johnson said that perhaps the age difference was due to the fact that adolescent girls watched less violent television programs. He cautioned that this hypothesis needed further investigation, however, because television programming has changed significantly since television viewing by the adolescent girls was assessed in 1983.

Johnson and his colleagues addressed the “chicken and egg” problem of whether television watching causes aggression, or people prone to aggression might watch more television.

They investigated whether individuals with a history of aggressive behavior were more likely to watch large amounts of television when they were a few years older. The authors found that was not generally the case, suggesting that heavy television watching leads to aggression, instead of vice versa.

Another task was to determine how much of the apparent link between television viewing and aggressive behavior was in fact due to television. The authors identified six other kinds of adversities that were most common among the study subjects who watched large amounts of television and committed violent acts.

Within each category of television-watchers, the authors analyzed the rates of violence among those who had experienced each of the other factors and those who hadn’t. If the rates were the same in both groups, for example, it indicated that that experience didn’t contribute to aggressive behavior. The researchers used a computer program to
calculate how much of the aggressive behavior was caused by factors other than television watching.

According to their results, 5.7 percent of the adolescents who watched less than one hour committed aggressive acts against other people in later years. In contrast, 22.5 percent of the adolescents who watched between one and three hours a day did so, as did 28.8 percent of the adolescents who watched more than three hours a day.