A number of major changes in sleep occur across puberty, including progressively later bedtimes and becoming more evening-type. This often results in truncated sleep on school mornings and later, longer sleep on weekends. Evening use of technologies with blue-rich screens can further delay sleep. In international studies, sleep loss in teens is associated with lower academic performance, lower self-esteem and higher incidence of depressive symptoms, increased substance use, being overweight, and increased risk of physical injury and road traffic crashes. However, the problems associated with adolescent sleepiness tend to go unrecognised because they are so common that they are considered normal.
Two surveys with Wellington High School students (years 9 and 12) in 1999 and 2008 highlighted changes in sleep timing across puberty, confirmed the value for the senior school of delaying school start time by 1.5 hours (making the first period of the day a study period), and revealed the increasing impact of technologies in the bedroom, particularly among students in the junior school whose 9 am start time had not changed.
A new study lead by Dr Lora Wu is comparing the timing of the evening melatonin rise (a marker of the circadian body clock cycle) in students from different schools whose first class starts before 9 am versus after 10 am.
