Watching TV involves an intricate web of tasks. Your body's relaxed, brain tuned in, eyes fastened to the screen. So what happens when it's time for the body to relax, the brain to tune out, and those eyes to close when you go to sleep at night? Several studies have revealed a relationship between heavy television viewing and sleep problems. These researchers investigated that relationship in teenagers and young adults in a long-term study.

What the researchers wanted to know: Is watching TV associated with sleep problems in teenagers and young adults?

What they did: A randomly chosen group of 759 mothers and their kids in upstate New York were interviewed (separately) three times–when the kids were 14, 16, and 22 years old. Interviewees answered questions about the kids' TV watching and sleeping habits and gave information on the parents' socioeconomic status, education, psychiatric condition, and possible child neglect.

What they found: Teenagers who watched at least three hours of TV a day were at a much higher risk for sleep problems–i.e., trouble falling asleep or waking up at odd hours and being unable to fall back asleep–when they entered young adulthood. This relationship was stable even when sex, age, socioeconomic status, education, psychiatric condition, and other factors were taken into account. The good news: 14-year-olds who watched a lot of TV but later cut their watching down to an hour a day lessened the risk of having sleep problems when they were older.

What this study means to you: Yet another clue that too much TV isn't good for you.

Caveats: The study didn't look at what programs the teens were watching, so there's no way to tell whether the nature of the TV shows had an effect on sleeping. Also, the researchers had hypothesized that late-night TV watching would increase the risk of sleep problems, but since they didn't ask what time of day the kids had been watching TV, that hypothesis couldn't be tested.

Find out more: Or go outside more: www.kids.gov/k_rec.htm

Read the article: Johnson, J.G., et al. "Association Between Television Viewing and Sleep Problems During Adolescence and Early Adulthood." Archives of Pediatrics and Adolescent Medicine. June 2004, Vol. 158, pp. 562-568.