"Those who prefer later bedtimes appear to exhibit more antisocial behavior than those who like to wake early and participate in daytime recreational activities, researchers report."

""A preference for evening activities and staying up late is related to problem behavior and is evident even in preteens," study co-author Dr. Elizabeth J. Susman, of Pennsylvania State University, told Reuters Health."

"Staying up late "contributes to lack of sleep and this, in turn, causes problems such as lack of control and attention regulation, which are associated with antisocial behavior and substance use," Susman added in a university statement."

"Susman and her team investigated the relationship between a preference for morning versus evening activities and antisocial behavior in 111 subjects between 8 to 13 years old. They also correlated morning to afternoon cortisol levels with behavior and noted the age at which the subjects reached puberty. "

"The researchers found a number of factors were related to antisocial behaviors in the study group, particularly in the boys who tended to exhibit more rule-breaking behaviors than did their peers. The findings are published in the Developmental Psychology journal."

"For girls, a preference for evening activities was associated with a higher incidence of relational aggression or aggressive behavior towards their peers."

"Boys who experienced prolonged high levels of cortisol -- smaller decreases in cortisol levels from the time of awakening until 4 pm -- tended to have more behavior problems than did their peers, the report indicates. The association was not true for girls, however."

"Normally, levels of cortisol, the stress hormone associated with circadian rhythms, peak in the morning upon awakening and plateau during the afternoon
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