Sleep patterns linked to teen behaviour

Sleep patterns linked to teen behaviour
http://www.stuff.co.nz/stuff/4135180a7144.html
Reuters Saturday, 21 July 2007

New study findings suggest that a preference for night-time over daytime activities may be associated with anti-social behaviour in adolescence, even in children as young as eight-years-old.

Those who prefer later bedtimes appear to exhibit more anti-social behaviour 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 behaviour and is evident even in pre-teens," 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 anti-social behaviour 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 anti-social behaviour in 111 subjects between eight to 13-years-old. They also correlated morning to afternoon cortisol levels with behaviour and noted the age at which the subjects reached puberty.

The researchers found a number of factors were related to antisocial behaviours in the study group, particularly in the boys who tended to exhibit more rule-breaking behaviours 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 behaviour towards their peers.

Boys who experienced prolonged high levels of cortisol - smaller decreases in cortisol levels from the time of awakening until 4pm - tended to have more behaviour 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 and evening hours.

Abnormalities in cortisol secretion, have also been associated with clinical depression and anti-social behaviour in earlier studies, the researchers note.

Boys who hit puberty at earlier ages tended to also engage in more rule-breaking and attention behaviour problems than did other boys, according to parent reports, and they self-reported more symptoms of conduct disorder.

Girls who were younger at puberty reported more relational aggression compared with their peers, study findings indicate.

Overall, the findings imply that "caregivers should be vigilant to bedtime activities of children and young adolescents," according to Susman.

"Monitoring these activities is essential for making sure that children and adolescents are going to sleep in time to assure enough sleep for good functioning in school and otherwise," she added.