This Canadian Study found that "one in four Canadian children are not developmentally ready for school by the time they start kindergarten, and that  excessive screen time may be a key contributor".  The study found that children were watching television or using digital devices for an average of 2.4 hours a day at age two, 3.6 hours at age three, and 1.6 hours at age five.  The article references back to a statement (posted here earlier) released by Britain’s Royal College of Paediatrics and Child Health stating there is “essentially no evidence” to support the popular idea that screen time is directly “toxic” to one’s health.

Dr Madigan says about her study: "“We can’t say that increased screen time causes delays in child development, but I think we get as close as we can, in an observational study, [to] saying that there is a link here, and it’s something we really need to pay attention to.”

It's an interesting read....and the debate continues.  

Study links excessive screen time to developmental delays in children