We already know that sitting and slouching is common with handheld device use. This slouching has given rise to the condition named "text neck" and causes neck pain, back pain, shoulder pain, and headaches.
We know that increased handheld device time is causing more nearsightedness.
We know that increased screen time promotes a sedentary lifestyle, which in turn promotes the development of obesity.
And so on.
Last week a Huffington Post article made controversial headlines because of a bold claim that children under 12 should never use handheld devices. Ever. And the author of the article didn't even mention text neck! Here's a quick excerpt.
The American Academy of Pediatrics and the Canadian Society of Pediatrics state infants aged 0-2 years should not have any exposure to technology, 3-5 years be restricted to one hour per day, and 6-18 years restricted to 2 hours per day (AAP 2001/13, CPS 2010). Children and youth use 4-5 times the recommended amount of technology, with serious and often life threatening consequences (Kaiser Foundation 2010, Active Healthy Kids Canada 2012). Handheld devices (cell phones, tablets, electronic games) have dramatically increased the accessibility and usage of technology, especially by very young children (Common Sense Media, 2013). As a pediatric occupational therapist, I'm calling on parents, teachers and governments to ban the use of all handheld devices for children under the age of 12 years.
In case her argument doesn't seem strong enough, she also has a Fact Sheet available which is, well, impressively exhaustive. I encourage everyone with children to check out the research and to form your own conclusions.