Too much time spent watching TV and playing computer games can hold back the development of young children, new research suggests.
A study of 2,400 Canadian children found more screen time was linked to lower scores in "milestone" tests of communication, problem solving, interpersonal skills and physical co-ordination.
The amount of time two and three-year-olds devoted to screen-gazing had a negative effect on their performance at three and five.
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There was no evidence children with developmental problems were allowed more screen time by their parents to control challenging behaviour.
Writing in the journal 'Jama Pediatrics', the team of Canadian psychologists concluded: "The present study examined developmental outcomes during a critical period of growth and maturation, revealing that screen time can impinge on children's ability to develop optimally."
The effect of screen time on children is a hotly debated topic and so far the jury has been out on how significant an impact it has.
In this study, the findings suggest too much screen time really can hold back children, the researchers said.
They pointed out that child development "unfolds rapidly in the first five years of life".
"When young children are observing screens, they may be missing important opportunities to practice and master interpersonal, motor and communication skills."
The study found that overall, children watched screens for an average of 17.09 hours per week at age two, 24.99 at age three, and 10.85 at age five.
Screen-gazing is a sedentary activity that reduces time available for walking and running, which may delay motor skill development, the researchers said.
