Young children who spend lots of time in front of TV and computer screens have high levels of psychological distress, and being physically inactive may make matters worse, new research published in the journal Pediatrics shows.

Most studies of "screen time" and mental health have been in adolescents and teens, Dr. Mark Hamer of University College London, the lead researcher on the current investigation, told Reuters Health. Hamer's group included children as young as 4 years old in their study.

"We replicated the earlier findings in older adolescents that show too much TV and screen-based entertainment is associated with poorer measures of mental health," Hamer said in an interview.

To determine if TV and screen entertainment time and physical inactivity have independent effects on psychological well-being, Hamer and his team evaluated 1,486 boys and girls 4 to 12 years old. The children's parents completed a test called the Strengths and Difficulties Questionnaire that assesses childhood mental health issues, such as hyperactivity, emotional symptoms, conduct problems and peer problems.

About 1 in 4 of the children logged at least 3 hours of screen time daily, while 4.2 percent had abnormally high scores on the questionnaire, indicating high levels of psychological distress. Kids with more than 2.7 hours of screen time daily had 24 percent higher scores on the test, signaling more distress, than kids who had less than 1.6 hours of daily screen time. Heavy TV and computer use plus low physical activity further increased distress scores by 46 percent.

Children started to show worse mental health at the highest screen time level, which was around 3 hours a day, Hamer noted. He and his colleagues point out that the American Academy of Pediatrics recommends limiting screen-based entertainment time to less than 2 hours. Current guidelines generally advise that kids spend at least an hour in active play daily, the researcher added.

"I think it's really a question of sort of limiting screen-based activity and just trying to encourage more physical activity," Hamer said. "That's the key message."

"There's also good evidence to suggest that physical activity levels actually reduce as children go through adolescence," he added, making it even more important for parents to help kids establish healthy habits early in life.