A propensity for activities in the evening rather than in the morning may offer clues to behavioral problems in early adolescence, according to psychologists who have found that kids who prefer evenings are more likely to exhibit antisocial behavior, rule-breaking, and attention problems.
Results from the study further suggest that atypical secretions of the hormone cortisol and early puberty are both linked to antisocial behavior, though the findings are stronger for boys than girls.
Elizabeth J. Susman, the Jean Phillips Shibley professor of biobehavioral health at Penn State, and her colleagues are trying to understand how a characteristic titled 'morningness/eveningness', along with the ratio of cortisol readings taken in the morning and afternoon, influences young adolescent behavior.
"Morningness/eveningness refers to individual differences in sleep-wake patterns and preferences for activity and alertness during mornings or evenings," Susman said. Previous studies with older adolescents show that it is linked to various psychological problems.
Susman thinks eveningness could make young adolescents vulnerable to antisocial behavior as well, and is studying how atypical patterns of cortisol secretion might add to the problem.
In humans, this hormone is responsible for regulating various behavioral traits such as the fight-flight response and immune activity that are connected to sensory acuity and aspects of learning and memory.
Cortisol normally spikes in the morning and falls to a plateau by afternoon and evening. Readings taken in the morning and afternoon usually show a significant drop, and scientists associate small differences in the readings with clinical depression and antisocial behavior.
The current study analyzed the preference for morning or evening activities among 111 boys and girls aged 8 to 13. Researchers then collected cortisol readings from saliva, and assessed the kids for a host of undesirable behavioral traits.
Results from the study suggest that a preference for eveningness is associated with traits of antisocial behavior such as rule-breaking, attention problems, and conduct disorder. However, these antisocial traits were seen only in boys.
"In girls, eveningness is associated just with relational aggression," said Susman. "This is behavior specifically meant to hurt another child's friendship, or feelings of isolation."
When the researchers factor in early puberty, the study finds that though it does not affect either the preference for mornings or evenings, or the cortisol ratio, earlier puberty is related to more antisocial behavior in boys, and relational aggression in girls.
"The link between eveningness preference and antisocial behavior was previously associated only with older adolescents," noted Susman, whose findings appear in the July 2007 issue of Developmental Psychology. "The novel finding of the study is that the link is now apparent as early as 8 year old kids."
Such early development of a preference for eveningness might have serious implications in later life, according to the researchers.
"Eveningness 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," the Penn State researcher added. Parents need to be vigilant in recognizing early signs of eveningness, and not only encourage their kids to sleep early but also ensure they get the required amount of sleep, Susman noted.