Children who watch too much TV or have a television set in their bedroom may suffer in school and cut their chances of graduating from college, according to new research.

Three separate studies provide new evidence that children’s television viewing habitscan have a negative effect on their academic achievement later in life in many ways. These include:

—Having a TV in the bedroom was linked to lower scores on standardized math, language, and reading tests in the third grade.

—Children who watched the most TV between the ages of 5 and 11 were less likely to graduate from college.

—Each hour of daily television viewing before age 3 was associated with lower developmental scores at ages 6 to 7.

Researchers say the impact of the findings could be substantial, as more than 70 percent of U.S. children have a TV in their bedroom.

Excessive television viewing among children has been linked to a greater risk of obesityand violent behavior. Researchers say the long-term effects of television on academic achievement have been less clear.

Read Web MD's "Too Much TV May Make Kids Bullies."

TV in Child’s Bedroom Hurts Test Scores

The first of the studies, which appear in the July issue of the Archives of Pediatrics & Adolescent Medicine, looked at the relationship between children’s use of media (television and computers) and academic achievement in about 350 third-graders at six public elementary schools in northern California in 2000.

More than 70 percent of the children said they had a TV in their bedroom, and these children scored between seven and nine points lower on standardized math, reading, and language arts tests than those who didn’t have a television in their bedroom.

Overall, children with a bedroom TV watched an average of nearly 13 hours of television per week compared with an average of less than 11 hours per week among those without a bedroom television.

The study also showed that children who had access to home computers scored higher on these tests than those who didn’t have access to a computer at home.

"This study doesn't prove that putting a television in your child's bedroom will decrease his or her test scores, but it does add to the increasing evidence that it's not a good idea," says researcher Thomas Robinson, MD, associate professor of pediatrics at the Stanford University School of Medicine, in a news release.

"A television in a child's bedroom has become the norm," says Robinson. "From the parent's perspective, it keeps kids amused and out of trouble. But with this arrangement parents are giving up any control of how much and what their children are watching.”

Read Web MD's "Young Kids Can Learn to Kick the TV Habit."

TV Cuts Children’s College Chances

In the second study, researchers in New Zealand followed the television viewing habits of about 1,000 children for about 15 years and then collected information about their educational achievement at age 26.

The study showed that the average number of hours the children spent watching TV in childhood was a strong predictor of their level of achievement in later life.

For example, children who watched fewer hours of television between ages 5 and 11 were more likely to graduate college than those who watched the most television.

In addition, children who watched more television as teens were more likely to leave school without a diploma or other qualifications (the lowest level of academic achievement).

Researchers found these effects of television viewing on educational achievement remained significant, regardless of child’s intelligence, family socioeconomic status, and childhood behavioral problems.

Read Web MD's "Soaking Up the Media: Full-Time Job for Kids."

Too Much TV Too Soon Harms Development

In the third study, researchers examined the effects of watching TV at a very early age on children’s cognitive development later on.

Researchers compared standardized test scores in math, reading recognition, and reading comprehension in a group of nearly 1,800 6- and 7-year-olds with their TV viewing habits before age 3 and at ages 3 to 5.

The study showed that the children watched an average of 2.2 hours of television per day before age 3, and an average of 3.3 hours between ages 3 and 5.

Researchers found that each hour of daily TV time before age 3 was consistently associated with lower scores on all three developmental tests at ages 6 and 7.

However, television viewing at ages 3 to 5 years appeared to have a slightly beneficial effect on the children’s scores on reading recognition and short-term memory at age 6 and 7.

Researchers say many educational television programs are targeted at 3- to 5-year-olds and may explain this positive effect. But they say reading recognition and short-term memory were the most basic of the cognitive development skills tested in the study, which would mean that this potential beneficial effect is very limited.

Read Web MD's "Tips for Keeping Kids Busy in the Summer."

Type of TV Matters to Kids

In an editorial accompanying these studies, Ariel R. Chernin and Deborah L. Linebarger, PhD, of the University of Pennsylvania, say although these studies generally showed that children’s television viewing had a negative effect on academic achievement, more research is needed on the effects of specific types of television content on children.

"Most researchers in this field would argue that we have moved beyond a simple debate about whether TV use is good or bad (a debate that assumes that TV is a monolithic entity),” write the editorialists.

As suggested by the third study, they point out that other studies have also shown watching educational television had a beneficial effect on children’s academic achievement.

Therefore, the next step for researchers is to look at the long-term effects of both the content and context of children’s television viewing on academic achievement.

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By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Borzekowski, D., Hancox, R., Zimmerman, F. Archives of Pediatrics & Adolescent Medicine, July 2005; vol 159: pp 607-613, 614-618, 619-625. News release, Stanford University.