Violent images on television and in computer games can increase aggressive behaviour among young children. Researchers have found that violent imagery in the media had a "substantial" short-term effect on children's arousal, thoughts and emotions.
Kevin Browne and Catherine Hamilton-Giachritsis, from the University of Birmingham, analysed data from six North American studies, which looked at the effects of media violence on children. They found consistent evidence that young children who watched violent television, films and video games showed more aggressive play and behaviour.
The study, in The Lancet journal, showed that the effect was "small but significant", and more relevant for boys. The evidence was less consistent among older children and teenagers, and for long-term effects on all ages.
The review acknowledged that family and social factors were likely to affect a child's response to violent imagery. One UK study found that the effects of film violence are greater in young people from violent families. But the researchers found that violent imagery had an effect regardless of socio- economic status, intelligence and parenting, suggesting some of the influence is independent of other factors.
The authors said large samples were needed to find whether violence in the media leads to violent criminal behaviour. Professor Browne said: "Parents and care-givers may be recommended to exercise the same care with adult media entertainment as they do with medication or chemicals around the home.
"Carelessness with material that contains extreme violent and sexual imagery might even be regarded as emotional maltreatment of a child.
"There is an urgent need for parents and policy makers to take an educational rather than censorial approach. Parents and teachers can view age-appropriate violent material with children and help them critically appraise what they see. In this way care-givers can reduce the effect of violent imagery. Producers also need to recognise the potential effects of their violent images on vulnerable audiences who might not have the capacity or the will to see violence in the context of the story."
John Beyer, director of the television watchdog Mediawatch UK, said film and television had a part to play if the Government's aim of reducing anti-social behaviour and violence were to be reduced.