Watching television or playing video games close to bedtime can act like a jolt of caffeine to young children, making them more likely to experience difficulty falling asleep, nightmares, and daytime fatigue, a new study in the journal Pediatrics suggests. 

In the study, 28% of preschoolers who watched TV or played video games for at least 30 minutes after 7 p.m. had sleep problems most nights of the week, versus 19% of children whose TV and video-game use took place only before 7 p.m.

Children are supposed to be winding down at bedtime, and TV and video games may interfere with that process by overexciting kids and "amping up" their brains, says Michelle Garrison, PhD, the lead author of the study and a research scientist at the Seattle Children's Research Institute.

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Evening entertainment may also disrupt the nocturnal rise in melatonin, a hormone involved in the sleep-wake cycle. TV and computer monitors "can keep melatonin levels from rising normally because of the brightness of the screens," Garrison explains.

Violent programming and video games appeared to contribute to sleep problems as well, even if the kids watched or played them during the daytime. Thirty-seven percent of the children who were exposed to one hour or more of violent media per day had sleep problems, compared with just 19% of those who watched less than one hour (or none), Garrison says.

The link between violent entertainment and troubled sleep isn't unexpected, says Dr. Carol Rosen, medical director of the pediatric sleep center at Rainbow Babies & Children's Hospital in Cleveland.

"The purpose of your dreams is to take your experiences of the day, reprocess them, look at them again, think about them, organize them," Rosen says. "If your intake is very scary things, then you might not be surprised that fears develop and that you have night waking with difficulty falling asleep."

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The study included 612 children ages 3 to 5. Garrison and her colleagues asked the parents to keep a detailed diary of their child's media consumption over the course of one week, including the title, timing, and duration of each show or game. (To determine the level of violence, researchers consulted parental guidance ratings and actually analyzed specific shows and games.)

Slightly under one-fifth of parents said their children had at least one sleep problem, the most common of which was difficulty falling asleep. Others included waking repeatedly during the night, not being alert in the morning, daytime sleepiness, and nightmares.

On average, the kids spent 73 minutes per day in front of a TV or computer. The more time they spent watching TV or playing video games in the evening, the more likely they were to experience a sleep problem. And the same pattern held for violent shows and games.

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Watching nonviolent TV shows or video games during the day didn't seem to impact sleep, however, which suggests that parents can help prevent sleep problems by imposing some minor restrictions on their children's media use.

The American Academy of Pediatrics, which publishes Pediatrics, recommends that parents limit nighttime media use and refrain from putting TVs or computers in children's bedrooms. (Sure enough, in the study, sleep problems were especially pronounced among kids with TVs in their bedroom, who tended to watch about 15 minutes more evening TV than their peers.)

For her part, Garrison recommends that parents make the hour before bed a "screen-free" time. They should also pay close attention to ratings guidelines from groups such as the Motion Picture Association of America, since even seemingly harmless animated or slapstick violence geared toward children may be disturbing for a preschooler, Garrison says.

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"The bulk of violence wasn't from...TV meant for adults or teens," she explains. "It was from children's programming, but for slightly older kids. What's fine for a 7-to-10-year-old can be too overwhelming for a 3-to-5-year-old."

Dr. Roya Samuels, a pediatrician at Cohen Children's Medical Center, in New Hyde Park, N.Y., urges the parents she sees in her practice to establish familiar and predictable pre-bedtime rituals. "That usually includes family dinner time, shower or bath time, and reading a story in bed, so kids know what to expect next and their minds and brains start winding down as opposed to winding up," she says.