When it comes to media exposure at a young age, the expert bodies are clear. Media exposure should be avoided. That is because there is an association between media exposure in young age groups and behavioural outcomes, regardless of what the content of the show is.

The kinds of behavioural outcomes reported include aggressive behaviour and attention problems. Poor attention ability and aggression in children are labelled as externalizing problems. In addition, this term also includes hyperactivity, non compliance and attention difficulties.

It has been reported that 17 to 48 per cent of children aged three years or younger watch television with as many as 73 per cent of preschoolers watching two hours of television on a daily basis.

In this week's Archives of Paediatric and Adolescent Medicine is a study looking at exposure of television at both 24 months and between 24-36 months, and the outcome of these externalizing problems at 36 months.

The study was a prospective study in the Netherlands, and followed children after birth. There were more boys  (56.3 per cent vs 48.4 per cent girls) who had externalizing problems at 18 months of age. The researchers then looked at the effects of TV exposure time and content at 24 months on the incidence of externalizing problems.

Interestingly, exposure time of more than one hour daily at 24 months alone, did not predict the outcome of externalizing problems at 36 months nor did watching unsuitable programs at 24 months of age.

However, when the pattern of TV exposure was looked at between 24 and 36 months,  overall high TV exposure was associated with incident externalizing problems. Continued high exposure also predicted as well  the same outcome.

Next the researchers looked at those children who already had externalizing problems when they entered the study. High TV exposure predicted the likelihood of the persistence of these problems.

Children develop their patterns of TV viewing very early in childhood and these patterns are then likely to be sustained. The researchers found that young children's continued exposure to television increases their risk for new onset externalizing problems and children who already had externalizing problems at 18 months, are  more likely to have persistent problems due to high increasing TV exposure early in childhood. There are theories as to why this outcome happens.

Content-based theories focus on the quality of programs. It is thought that children learn from the content they see using both cognitive and social learning mechanisms. In this study, the effect of content was not the indicator for externalizing problems. However the exposure to inappropriate content in the study was low and therefore this effect may not have been detected.

A second theory looks at displacement, meaning that time spent watching TV means less time for intellectual and physically stimulating activities. The images move too quickly for children to process the content and may have negative effects on attention abilities. In the study, a high level of exposure was a risk factor for both the onset and persistence of externalizing behaviours.

This study done over time showed that both sustained and excessive exposure posed a risk for developing behavioural problems in young children.What is worrisome is that these findings existed in a population where excessive TV viewing is low compared to North America.

Extensive exposure to media influences development, behaviour and day to day activities of young children. High levels of TV exposure increase the likelihood of developing externalizing problems in preschool children. Parents should be clear in discouraging young children's exposure to television.