The website MCV released an artcle about the relationship between violent video games and knife epidemic which was said by Boris Johnson mayor of london.
The details are as below:

Violent games encourage knife crime, says Boris Johnson
Mayor of London cites #DY#violent video games#DY# as an influence in rising knife epidemic
London Mayor Boris Johnson has pointed the finger at violent video games for being a cause of knife crime in the Capital.
In a piece railing against #DY#London#DY#s knife crisis#DY# written for thelondonpaper, the blunder-prone public figure writes: "We must show young people that knives are not cool, and for that we need positive role models."
"I want to counteract the damaging influences drug-addled celebrities and violent video games and the lure of the life in the gang by providing opportunities."
It#DY#s not the first time Boris has been critical of video games.
In January, 2007, he posted a piece on his website entitled #DY#The writing is on the wall, computer games rot the brain#DY#.

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Resource: MCV