(CNN) Use of screen time explodes between 12 months and three years in the United States, and most Canadian preschoolers between the ages of two and three are not meeting World Health Organization recommendations for appropriate use of television, computers and other screens, according to two new studies published Monday in JAMA Pediatrics.

Screen habits begin early

Nearly 4,000 upstate New York mothers were asked about the level of screen use by their children at 12, 18, 24, 30 and 36 months of age. Those answers were then compared to the results of similar questions when the children were 7 and 8 years old.

Researchers showed that daily use of television, computers and mobile devices by children increased three fold from age 12 months to three years, from an average of 53 minutes at 12 months to more than 150 minutes.

Children of first-time mothers and children who were in home-based child care logged the highest amount of screen time by elementary school, the study found.

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