Kids today are entertainment media junkies, spending more than 50 hours a week with their cell phone, music player or game console, according to a US study.

With technology allowing nearly 24-hour media access as children and teens go about their daily lives, the amount of time young people spend with entertainment media has risen dramatically, especially among minority youth, according to the study by the non-profit Kaiser Family Foundation. “Today, 8-18 year-olds devote an average of 7 hours and 38 minutes (7:38) to using entertainment media across a typical day (more than 53 hours a week). And because they spend so much of that time ‘media multitasking’ (using more than one medium at a time), they actually manage to pack a total of 10 hours and 45 minutes (10:45) worth of media content into those 7½ hours,” the study says.

“The amount of time spent with media increased by an hour and seventeen minutes a day over the past five years, from 6:21 in 2004 to 7:38 today. And because of media multitasking, the total amount of media content consumed during that period has increased from 8:33 in 2004 to 10:45 today.”

The increase in media use is driven in large part by ready access to mobile devices like cell phones and iPods. Over the past five years, there has been a huge increase in ownership among 8- to 18-year-olds: from 39% to 66% for cell phones, and from 18% to 76% for iPods and other mp3 players. During this period, cell phones and iPods have become true multimedia devices: in fact, young people now spend more time listening to music, playing games, and watching TV on their cell phones (a total of :49 daily) than they spend talking on them (:33).

Only about three in ten young people say they have rules about how much time they can spend watching TV (28%) or playing video games (30%), and 36% say the same about using the computer. But when parents do set limits, children spend less time with media: those with any media rules consume nearly three hours less media per day (2:52) than those with no rules.

“The amount of time young people spend with media has grown to where it’s even more than a full-time work week,” said Drew Altman, Ph.D., President and CEO of the Kaiser Family Foundation. “When children are spending this much time doing anything, we need to understand how it’s affecting them – for good and bad.”

There was also a notable decline in school performance among young people who were heavy media users. The study doesn’t claim a definite link, but notes that about half (47%) of heavy media users say they usually get fair or poor grades (mostly Cs or lower), compared to about a quarter (23%) of light users.

The report can be read in detail here.