Saturday morning cartoons may seem harmless enough, but allow preschoolers to watch some of the superhero and slapstick antics intended for kids a bit older and it could spell trouble for their sleep.
In a new sleep study from the Seattle Children's Research Institute, researchers found that kids between the ages of 3 and 5 had more nightmares, daytime fatigue and difficulty waking up when they watched violent programming or when they were allowed TV or computer time after 7 p.m.
What may come as a surprise to parents, however, is what qualifies as violent programming for a preschooler:
"Bugs Bunny counts as violence in this study, and so does Batman and so does Pokémon," lead author Michelle Garrison told MedPage Today/ABC News. "Slapstick funny violence in Bugs Bunny or superhero violence in Batman or more realistic violence -- we didn't see a difference in terms of the impact on sleep," she said.
Screen time has been associated with childhood sleep difficulties in the past, but this research is the first to look at the impact of different types of content, rather than just screen time itself, Garrison said.
The finding comes from week-long sleep diaries prepared by parents of 612 three-, four- and five-year-olds as part of a larger research project on sleep and media use. In the sleep diaries, parents reported how often the child had difficulty getting to sleep, woke up repeatedly, had nightmares, had difficulty waking in the morning or was tired in the daytime.
These media diaries found that the children were watching TV or using a computer about 73 minutes a day on average, although some scored more than four hours, Garrison and colleagues reported. That's less than what some other studies found -- reporting averages of two, three or even four hours in the same age group, she said.
Researchers also found that kids with a TV in their room racked up an additional 40 minutes of media time compared to kids without TVs in their bedrooms.
Bugs Bunny, Batman = Violence for Preschoolers
For the most part, children were not watching highly violent adult-oriented fare or playing shoot-em-up computer games. Instead, they were viewing material aimed at slightly older children, and not even that much of it, Garrison said.
"The amount of violence wasn't huge," she said -- an average of 19 minutes a day, but it had a significant effect on daytime fatigue, difficulty getting up in the morning and the frequency of nightmares in the children studied.
Even small amounts of age-inappropriate TV may have an impact on preschool-age children because their "cognitive ability to distinguish between reality and fantasy is not developed," said Dr. Jeannine Gingras, a pediatric sleep expert in Charlotte, N.C.
It also has to do with what the child perceive as frightening, even if it's not violent, she said. Clowns, for instance, can give many children nightmares, or kids' movies that seem benign to adults can disturb children.
"I had one [5-year-old] child who had horrible sleep difficulties" from watching "Monsters, Inc." -- a movie that most parents would assume is small-child appropriate, she said.