MONDAY, Nov. 1 (HealthDay News) -- Staying up late to play video games, surf the Internet and send phone text messages may lead to learning problems, mood swings, anxiety and depression in children, a pilot study suggests.

The research, conducted at the Sleep Disorders Center at JFK Medical Center in Edison, N.J., found that children who snuck time on their cell phones, computers and other electronic devices after supposedly going to sleep had a greater chance of sleep disorders that cause other difficulties.

"These activities are not sleep-promoting, like reading a novel or listening to music. They stimulate the brain and depress normal sleep cycles," said study author Dr. Peter G. Polos.

His team was scheduled to present the findings Monday at the American College of Chest Physicians annual meeting in Vancouver.

The study was based on a survey of 40 boys and girls with an average age of 14. The researchers focused on their activities after they had gone into their bedroom for the night and were supposed to be sleeping.

Participants reported an average of 34 texts per night after bedtime, and an average of 3,400 night-time texts per month. These texts occurred from 10 minutes to four hours after going to bed. The average participant was awoken once a night by a text.

Girls were more "text happy," while boys were more likely to stay awake playing video games, said Polos, a physician at the hospital and a clinical instructor at its Sleep Disorders Center. All of the participants had gone to the center for help with sleep problems.

The research found correlations between late-night electronic media use and attention-deficit/hyperactivity disorder, mood swings, anxiety, depression and poor cognitive functioning (thinking skills) during the day.

About half of the parents of study participants didn't know what the kids were up to, said Polos. The others knew, but had a fatalistic attitude.

"They [parents] thought, 'This is the world we live in, what can you do?'" said Polos. But parents need to monitor electronic media use, he said, because "at the end of the day, the parent is still the parent, the child is still the child."

Polos said doctors need to start asking children and teens routinely about night-time media use and talk to the child, along with the parents, about the negative consequences of poor sleep.

Calling America a "sleep-deprived culture," Polos noted that teens get little enough sleep "with sports, homework and getting up early for school." Late-night media use "really isn't helping," he said.

Expert Richard Gallagher said another reason parents need to monitor media use is to know what is going on in their children's lives.

"Parents need to take the perspective of what their own lives were like growing up," said Gallagher, director of the Parenting Institute at the Child Study Center at NYU Langone Medical Center in New York City.

Parents used to know who their children were talking to on the phone or hanging out with because it was all done in the real world when families typically had one or two phones, he noted.

"Parents knew if someone came to the door to see their daughter or son," said Gallagher, an associate professor of adolescent psychiatry at New York University, adding that "children should have some privacy, but parents need to make it more comparable to when they were growing up."

Parents need to set rules such as no computers in the child's bedroom, no phone calls during mealtimes, and establish a phone use curfew.

"Then have the kids turn over the phones," said Gallagher.

Gallagher also noted that the effect of media can be good for some children who have "more contact with others than they might normally have had" as a result. But parents also need to be aware that all the messages sent back and forth "aren't necessarily friendly, or about things they want their kids to constantly think about," he said.

Because many kids are messaging or texting throughout the day, "there is no break from any kind of drama," or peer-related problems their children might be having, said Gallagher.

Both experts said the long-term effects of children's constant use of technology is unknown and needs more study. Also, they both emphasized the need for parents to talk with their children, and start early.

Citing the example of a parent who resorted to turning off the router at night, Polos said it's important to get a jump on things before it becomes a big problem.

"By then, the horse is out of the barn," said Polos, when parents delay getting involved.

More information

For more on teens and texting, go to the Pew Research Center.