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Social media has changed the 
, for good and for 
. The USA's top doctor said one bad thing is it can cause mental health 
. Dr Vivek Murthy wants social media companies to put mental health 
 on their sites. He is worried about the 
 social media does to young people. He said youngsters see too much 
 sexual and violent content. Murthy said: "It is time to require a…
 label…stating that social media is associated with 
 mental health harms for adolescents." He said 
 were also needed to keep young people 
 online.