For parents who fret about the amount of time their kids devote to electronic media, consider this: In Ontario, hundreds of thousands of teens spend nearly seven hours a day staring at a computer or TV screen.
The number surprises even researchers familiar with this growing trend and is likely to take a serious toll not only on adolescents' physical health, but on their emotional and mental well-being as well.
"That's a lot of time spent in front of a screen being sedentary," said Robert Mann, a senior scientist at Toronto's Centre for Addiction and Mental Health, whose study revealed the new screen-time data. "That's almost a third of the day."
Public health officials such as the Canadian Paediatric Society recommend no screen time for children under two years of age and a maximum of two hours for children older than two.
The new statistic - 9.7 per cent of kids in Grade 7 to 12, or about 327,000 students, spend at least seven hours a day in front of a TV or computer - was released Monday as part of CAMH's annual Ontario Student Drug Use and Health Survey. (The drug data was released in November.) Dr. Mann, the study's co-principal investigator, says he was surprised by the results of the screen-time question, the first time it was included in the survey.
The study does not make a direct causal link between screen time - or "sedentary behaviour," as it sometimes calls it - and health issues. But in an interview, Dr. Mann said it's no coincidence that various indicators of physical health are simultaneously on the decline.
The survey found that the number of students who rate their health as poor has increased significantly over the past two decades, to 14.5 per cent from 8.9 per cent in 1999. More than a quarter of the students are either overweight or obese. And 8.5 per cent of students reported no physical activity in the seven days before the survey.
The study also did not connect screen time and long-term effects on mental health and cognitive function. But Dr. Mann noted that many of the students who logged long hours in front of a screen expressed feelings of unhappiness and experienced loss of sleep.
Other recent studies have linked screen time to adverse effects on social skills and attachments to peers and parents. (Speaking of parents, they're not in the clear either - emerging research has found that parents' use of technology is creating negative emotional effects in their children.) Just last week, a study published in the journal Pediatrics found TV and video-game use is associated with attention-span problems in schools.
There may also be a parallel between extreme electronic-media use and Internet addiction, says screen-time expert Dimitri Christakis, a professor of pediatrics at the University of Washington School of Medicine. The 10 per cent of adolescent heavy users is about the same percentage as estimates of North Americans who suffer from true Internet addiction, he says.
While there are social taboos around other addictive substances, such as alcohol and drugs, there's no such constraint on technology.
"If there is a genetic predisposition, which there probably is, because we're reaching a level of such high saturation … we are going to in fact ensure that everybody's who's susceptible goes on to develop an addiction," he said.
But researchers admit science is having a hard time tracking these risks, because the technology is moving so fast. (Dr. Christakis's current research is looking at whether changing the television diet of preschoolers can affect their behaviour and levels of aggression.) "We're not able to keep up with it. It takes us years to get a study funded, then years to conduct it and in the meantime, Twitter comes out," he said.
Nevertheless, he says, the emerging picture does give parents a reason to be cautious about how teens use media and to question exactly what they're not doing while they're staring at a screen. Chances are, it's connecting with their families, reading books, being active and getting enough sleep.
Yet parents and researchers alike have to resist lumping all technology use together. Texting is not the same thing as playing World of Warcraft, says Dr. Christakis.
There's nothing wrong with teenagers communicating with each other, he says. Much of the research on negative cognitive effects of screen time is linked to the pacing of the media; more stimulating, rapidly sequenced content is associated with delayed attention spans across the age spectrum.
"If you're writing long e-mails online, if you're penning 10-page love letters, there's nothing wrong with that. It's just displaced putting pen to parchment," he said. "That's fundamentally different in the way that it engages your brain and the effects it has than playing four hours of StarCraft."
All of which makes it a challenge when it comes to both parenting and public policy.
In a way, it would be easier if it was all bad, says Dr. Christakis. "If media were like cigarettes, we could just say, don't do it. But we can't."