Americans aged eight to 18 spend more than seven hours per day on average consuming media. (Julian Stratenschulte, Associated Press)

Children and teens spend about as much time with media as they do sleeping, and the overexposure could take a toll on their health, a new U.S. study suggests.

The study, reported in Monday's issue of the journal Pediatrics, showed Americans aged eight to 18 spend more than seven hours per day on average consuming both old media such as TV, movies and magazines as well as new media including internet, social networking sites, video and computer games and cell phones.

Dr. Victor Strasburger of the University of New Mexico reviewed studies on the combined effects of all the media consumption.

The study found exposure to the media can make children more prone to:

• Violence — the impact of media violence on real-life aggressive behavior is 0.31 times higher, compared with 0.39 times for the link between smoking and lung cancer.
• Early and unprotected sexual activity, particularly if exposed to pornography.
• Alcohol and tobacco consumption, with exposure to smoking in movies in Grades 5 to 8 predicting the likelihood of starting smoking within eight years.
• Obesity, with possible culprits including the marketing of junk food and fast food and the tendency to eat while watching media.
• Heavy television-viewing — that is, two to three hours a day in early childhood has been linked with attention-deficit disorder during the early school years, though experts disagree about the nature of the connection.

Condom lesson

Television shows geared toward teenagers actually have more sexual content — 6.7 sex-related scenes per hour — than adult-oriented prime time shows with 5.9 scenes per hour, yet there is little mention of the need for contraception or for responsibility on top teen shows, the researchers said.

When contraception is mentioned, however, it may help to educate viewers. In an episode of Friends cited by researchers in 2003 for example, Rachel told her boyfriend Ross she was pregnant although they had used a condom. A national telephone survey conducted after the episode suggested adolescents learned condoms are not fool-proof, and as a result they were more likely to discuss contraception with their parents, the study's authors said.

And in 2008, the Kaiser Family Foundation pointed to an episode of Grey's Anatomy taught viewers about HIV and pregnancy.

Strasburger and his coauthors concluded parents should play a role in their children's media consumption by:

• Limiting the amount of time spent using media, particularly for children under two years old, to less than one or two hours per day.
• Keeping media devices out of youths' bedrooms.
• Watching media with their children and discussing the content.

"To date, too little has been done by parents, health-care practitioners, schools, the entertainment industry, or the government to protect children and adolescents from harmful media effects and to maximize the powerfully prosocial aspects of modern media," the study's authors concluded.

"More research is needed, but sufficient data exist to warrant both concern and increased action."

They noted that media offer a communication and education tool to convey and encourage healthy attitudes and behaviours, such as teaching children empathy and tolerance. Video games have also helped improved compliance with taking chemotherapy among teens with cancer.