Daily television viewing for two or more hours in early childhood can lead to behavioral problems and poor social skills, according to a study of children 2.5 to 5.5 years of age conducted by researchers at the Johns Hopkins Bloomberg School of Public Health.

The Hopkins researchers found that the impact of TV viewing on a child’s behavior and social skills varied by the age at which the viewing occurred.

More importantly, heavy television viewing that decreased over time was not associated with behavior or social problems.

The American Academy of Pediatrics recommends that children under age 2 watch no television while children age 2 and older are limited to no more than two hours of daily viewing.

The study is published in the October 2007 issue of Pediatrics.

“A number of studies have demonstrated negative effects of heavy television viewing. However, timing of exposure is an important consideration as reducing viewing to acceptable levels can reduce the risk of behavioral and social problems,” said Kamila Mistry, MPH, lead author of the study and a doctoral candidate in the Bloomberg School’s Department of Population, Family and Reproductive Health.

For the study, the research team analyzed data for 2,707 children collected from the Healthy Steps for Young Children national evaluation. Parents were surveyed about their child’s television viewing habits and behavior at 2.5 and at 5.5 years of age.

Sixteen percent of parents reported that their children watched two hours or more of television daily at 2.5 years of age (early exposure), while 15 percent reported that their children watched two hours or more of television daily at 5.5 years of age (concurrent exposure).

One in five parents reported that their children watched two hours or more of television daily at both 2.5 years and at 5.5 years of age (sustained exposure).

However, early exposure that was subsequently reduced was not a risk for behavior problems.

The study also found that having a television in the child’s bedroom at 5.5 years of age was associated with behavioral problems and poor sleep. Forty-one percent of the children included in the study had a television in his or her bedroom.