Associations between friends' disordered eating and muscle-enhancing behaviors

► Study uses data provided by friends to test associations between adolescents' and their friends' muscle-enhancing behaviors in the US. ► Study uses data provided by friends to test associations between friends' and males' disordered eating behaviors. ► Adolescents' use of these behaviors is associated with their friends' use of the same behaviors. ► Males' steroid use and use of other muscle-enhancing substances were particularly strongly related to their friends' use. ► Friends may be a critical component in the development of effective intervention programs.