The study is published in the journal Acta Pedatricia this month. It looks at past research into the effects of DVD and television viewing on young children's language and cognitive development.
Its author, Professor Dimitri Christakis of the Seattle Children's Research Institute, warned, 'Parents should exercise due caution in exposing infants to excessive media.' He said too much TV viewing has a 'real potential for harm'.
Professor Christakis has spent 11 years researching the effects on children's development of watching TV programmes and infant DVDs such as 'Baby Einstein' and 'Brainy Baby'.
He hoped the study might raise parental and professional awareness of the relatively new phenomenon of IQ-boosting programmes, and said that manufacturers relied on parental testimonials rather than scientific evidence to sell infant DVDs, without any robust evidence to prove they are beneficial to an infant's brain.
Professor Christakis cited a 2007 study which found that children aged between seven months and 16 months knew on average six to eight words fewer after an hour's DVD viewing.
He pointed to a possible link between television and the development of ADHD through over- stimulation of an infant's brain, and said that more research should be done to understand the true effect that media can have on a child's language and cognitive development.
Liz Attenborough, manager of the UK campaign Talk To Your Baby, run by the National Literacy Trust, said, 'Though there are reports on the issue that paint a potentially worrying picture for parents, for most families it is unrealistic to expect that children will not see television at all.
'It is more realistic to advise that parents limit the time that children spend in front of the TV, and that children have adult company while watching programmes or DVDs.'
