Adolescents who experience sleep problems and longer sleep duration are more reactive to stress, which could contribute to academic, behavioural and health issues, says a new study. ‘This particular population is more likely to experience insufficient sleep, and their functioning is more negatively affected by lower sleep quality,’ said one of the researchers Sylvie Mrug, psychology professor at the University of Alabama at Birmingham in the US. The researchers examined two dimensions of sleep -- sleep duration and sleep problems from the perspectives of adolescents and their parents, as well as the levels of the stress hormone cortisol before and