In an interesting study of adolescent sleep patterns, Crowley and Carskadon, of Rush University Medical Center in Chicago, examined melatonin rhythms in a group of adolescents who were assigned to sleep later and sleep more than their typical weekday pattern[1]. Mimicking the common pattern of many adolescents who are relatively sleep deprived during the school week but who compensate by lengthening and delaying their sleep schedule during the weekend, these investigators measured the timing of melatonin secretion (dim light melatonin onset) in subjects who had this typical delayed, extended pattern, in subjects who had an afternoon nap condition, and in subjects who received one hour of bright light on awakening.  Consistent with their expectations, they found that melatonin rhythms were delayed in all conditions and that bright light therapy was ineffective in correcting this delay.

This research confirms that the delayed, extended weekend sleep hours of adolescents are associated with actual delays in the timing of melatonin secretion.  Delays of this kind are frequently associated with depression[2].  Whether these weekend phase shifts increase the risk for depression or mood instability is not known.  Publications of this kind nonetheless sensitize us to the biological, psychiatric, and public health implications of how standard and uniform school schedules interact with the constitutional timing preferences (chronotypes) of late-sleeping adolescents.

1.            Crowley, S.J., et al., Modifications to weekend recovery sleep delay circadian phase in older adolescents. Chronobiology International, 2010. 27(7): p. 1469-92.

2.            Lewy, A.J. and A.J. Lewy, Depressive disorders may more commonly be related to circadian phase delays rather than advances: time will tell. Sleep Medicine, 2010. 11(2): p. 117-8.