Munich -- Juvenile crime and failure at school do correlate with the amount of time a youth spends playing violent computer games, according to a German study which challenges the conventional wisdom that the games are harmless, a report has concluded

A school psychologist in Munich, Werner Hopf, surveyed 653 schoolboys over two years, the Hamburg-based magazine Geo Wissen reported.

Playing the games, in which boys pretend to maim and kill, was the best predictor of which boys would get into trouble with police, though other predictors included family poverty, bad relationships with parents or growing up among criminals.

Boys playing violent games were far more likely to be charged with assault, vandalism, bullying and theft from vending machines and also gained worse marks at school. Watching violent movies was not so strongly linked to delinquency.

School massacres in Germany by boys who played such games have prompted public debate about banning "first-person shooter" games, but civil-liberties groups and the games industry have denied any significant linkage. No legislation has been passed.

First person shooters are often the most popular titles on the market. Last week the much hyped Grand Theft Auto IV was released in Germany. The series is famous for its casual attitude to crime and killing, encouraging the player to steal cars and kill people to complete missions.