Children and adolescents who watch a lot of television are more likely to become involved in antisocial and criminal behaviour as adults, a University of Otago study indicates.
One of the study co-authors, Associate Prof Bob Hancox, said the research showed the issue of excessive television watching needed to be "taken seriously".
Researchers found the risk of a criminal conviction by early adulthood increased by about 30 per cent with every hour children spent watching TV on an average week night.
And watching more television in childhood was associated, later, with aggressive personality traits and an increased tendency to experience negative emotions.
There was also an increased risk of developing an antisocial personality disorder; a psychiatric disorder characterised by persistent patterns of aggressive and antisocial behaviour, the study found.
Prof Hancox said the study "provides further evidence that excessive TV watching can lead to poor behaviour".
The study, co-authored by Lindsay Robertson, Prof Hancox and Dr Helena McAnally, of the Otago preventive and social medicine department, was published online by the US journal Pediatrics.
The study followed 1000 children born in Dunedin in 1972-73 who are part of the Dunedin Multidisciplinary Health and Development Study.
Every two years between 5 and 15, they were asked how much television they watched. They watched an average of 2.3 hours on weekdays.
The researchers found the relationship between TV viewing and antisocial behaviour was not explained by socioeconomic status, aggressive or antisocial behaviour in early childhood, or parenting factors.
Mosgiel resident Gina Aitken, whose family is not involved in the study, said her three children were all keen television viewers.
But they also had a wide range of interests, including sports, reading and socialising.
Mrs Aitken agreed with the idea of limiting viewing, and said homework was a priority on week nights and extra reading was encouraged at home.
The study could not clarify what might contribute to the adverse effects but watching too much violence could be a factor.
And too much television could also adversely affect homework, potentially contributing to poorer educational, employment and life outcomes.
The American Academy of Pediatrics recommends children should watch no more than 1 to 2 hours of quality television each day.