Too much TV may be bad for a child’s brain

October 2005

The effects of television may be more harmful to a child’s development than doctors, educators and parents previously suspected. A number of studies have found that television viewing impedes cognitive development and lowers standardized test scores and academic success.

Although some argue that there is television programming that can facilitate children’s cognitive and academic development, research shows that most children are not watching those programs. Even those programs may have damaging results on children’s development. Three studies published in the Archives of Pediatrics and Adolescent Medicine discuss these data and the possible long-term effects early television viewing can have on children.

“A small amount of television — no matter what kind — will have minimal adverse effects on children, but a very large amount, even good programming, can be detrimental to children’s development,” Frederick J. Zimmerman, PhD, told Infectious Diseases in Children. “Even Sesame Street, a wonderful show for preschoolers – has been shown to have adverse effects on language development among 1-year-olds.”

Cognitive outcomes

In the first study, Zimmerman and Dimitri A. Christakis, MD, MPH, of the University of Washington, Seattle, tested the independent effects of television viewing in children younger than 3 using data from the National Longitudinal Survey of Youth.

The study population consisted of 1,797 children who were approximately 6 years old. Researchers used those participants with complete data at the time of one of the four most recent survey interviews (1994, 1996, 1998 or 2000) as the study sample. Researchers compared mathematics, reading recognition and reading comprehension scores of 6- and 7-year-olds from the Peabody Individual Achievement Test (PIAT) with the amount of time those children spent in front of the television before age 3 and from ages 3 to 5.

Each hour of average daily television viewing before age 3 was associated with detrimental effects on various standardized tests, including the PIAT Reading Recognition Scale of .31 points (95% CI, -0.61 to -0.01 points), Reading Comprehension Scale of .58 points (95% CI, -0.94 to –0.21 points) and the Digit Span -0.10 points (95% CI, -0.20 to 0 points).

There were, however, some positive outcomes in reading comprehension from television viewing in children between the ages of 3 and 5. Researchers noted 0.51 points improvement (95% CI, 0.17 to 0.85 points) and short-term memory improvement.

“Television is not inherently good or inherently bad, but rather it is what you make of it. Television is a tool, a powerful tool designed by adults, and like many such tools, it can be dangerous,” said Zimmerman. “Context is also crucial. Part of context is what parents say — either implicitly or explicitly — about television to their children. Parental involvement cannot turn a bad show into a good one, but it can turn a limited amount of viewing of bad material into a neutral, not harmful, experience for the child.”

Children between ages 3 and 5 in Zimmerman’s study watched an average of two or more hours of television or videos per day.

Academic effects

Early television viewing may have long-term detrimental effects as well, according to another study in the journal by Robert J. Hancox, MD, from the University of Otago in Dunedin, New Zealand. Hancox and colleagues examined the associations between early television viewing and educational achievement later in life.

Researchers in that study followed 1,000 children born between April 1972 and March 31, 1973. The researchers collected data on the children at the following ages: 5, 7, 9, 11, 13 and 15. They conducted follow-up when the children were 26. Ninety-six percent of the living cohort participated in follow-up; researchers measured outcomes of educational achievement.

At ages 5 and 11, the children reported watching television for a mean of 2.06 hours (SD, 0.82 hour) on weekdays. At ages 13 and 15, they reported watching television for 3.13 hours per weekday (SD, 1.43 hours). Overall, the mean weeknight viewing times between 5 and 15 years of age were 2.43 hours (SD, 0.85 hours) for boys and 2.24 hours (SD, 0.89 hour) for girls.

The researchers found that the mean time spent watching television during childhood and adolescence was significantly associated with leaving school without qualification and negatively associated with attaining a university degree.

Although television viewing in children between 5 and 11 years old and in teenagers between 13 and 15 had adverse associations with later educational achievement, adolescent viewing was a stronger predictor of leaving school without qualification, whereas childhood viewing was a stronger predictor of nonattainment of a university degree.

The researchers did not note any significant interactions between sex or socioeconomics and television viewing. They did, however, note an interaction between television viewing hours and IQ for attaining a university degree that was of borderline statistical significance (P = .08).

“Our data [suggest] that those who watched the least [television] got the best educational qualifications, and it is not realistic to expect children to choose the ‘right’ programs themselves,” Hancox told Infectious Diseases in Children. “While we found no evidence of a positive effect at any age, some researchers strongly believe that watching age-appropriate educational programs are helpful.”

Test scores

According to another study in the journal, poorer academic achievement among frequent television viewers extended to younger grades as well. Dina Borzekowski, EdD, lead researcher and assistant professor in the department of population and family health at Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues, from Stanford University in Palo Alto, Calif., noted school achievement test scores were significantly lower in children who have televisions in their bedrooms compared with children who do not. Computers in the homes of students, however, were associated with higher test scores.

Borzekowski’s study included a diverse group of third-graders from six schools in northern California. Nearly 400 students and their parents reported on the types of media available in their homes, including computers, televisions and video games, and how often the child used them. Researchers used the Stanford Achievement Test twice over the year to test language arts, math and reading skills.

Children who had televisions in their bedrooms scored an average of eight points lower on math and language arts tests and seven points lower on language tests, even when the researchers controlled for parents’ education level, the amount of media used per week and gender, researchers said. They also found that children with access to a computer in the home scored an average of six points higher on the math and language arts test and four points higher on the reading test.

Future consequences

Researchers are still not certain how television creates negative and positive changes in children. Zimmerman and colleagues believe that the content on television may be detrimental to children’s cognitive development. Television may also simply replace the activities that children younger than 3 would do that are beneficial to cognitive development such as imaginative free play and interaction with adults.

Another possibility is the intense visual and aural stimuli of television may cause adverse effects to the development of children’s brains.

Researchers said they cannot rule out the possibility of reverse causation in these studies. Television viewing may be one of the preferred activities of children and adolescents who are not academically motivated, the researchers said.

The possibility that a medium frequently used by children has farther reaching effects than most parents are aware of is alarming. Researchers warn parents to adhere to the AAP’s recommendations. “In short, less television is better, aim for below an hour a day on average. Try to be aware of what they are watching,” Hancox said.

For more information:

• Borzekowski DLG, Robinson TN. The remote, the mouse, and the no. 2 pencil”; The household media environment and academic achievement among third grade students. Arch Pediatr Adolesc Med. 2005;159:607-613
• Hancox RJ, Milne BJ, Pulton R. Association of television viewing during childhood with poor educational achievement. Arch Pediatr Adolesc Med. 2005;159:614-618.
• Zimmerman F, Christakis DA. Children’s television viewing and cognitive outcomes. Arch Pediatr Adolesc Med. 2005;159:619-625.