Callous-unemotional traits are associated with a distinct neurobiology (4) and associated with a variety of indications of particularly poor prognosis for, and a severe form of, Conduct Disorder (2). Children with Conduct Disorder are less likely to be inhibited from acting aggressively, including using a gun, they lack the typical aversive emotional reaction that healthy individuals typically experience when thinking about or engaging in actions that hurt other others (4). 

Peer gun carrying has been shown to be one of the strongest predictors of adolescent gun use (6). Yet, the data from the Robertson et al paper show that this predictor is only significant for those with low to medium level of callous-unemotional traits.