The call from mental health experts follows research showing a link between crime and low levels of the stress hormone cortisol in teenage boys. Academics at Cambridge University took saliva samples from boys with a history of antisocial behaviour and found in many cases their bodies produced only low levels of cortisol, which helps to regulate emotions in stressful situations. Marjorie Wallace, chief executive of mental health charity Sane, said the research was welcome as it helps view antisocial behaviour "as a health issue, rather than purely...