Sleep deprivation and late bedtimes are, of course, big problems in teens' sleep. However, there are other problems that are widely observed in the adolescent population. One of the most problematic ones is sleep debt. Most teens follow a pattern of sleeping less during the week and sleeping in on weekends to compensate. Though many believe this helps reverse the effects of lack of sleep during the week, research proves it clearly doesn't. Firstly, many teens do not sufficiently recover in the weekend and end up fatigued in the following week again. Additionally, shifting patterns on the weekends such as late nights with friends followed by late mornings in bed do not match the weekday rhythm, creating what Carskadon refers to as the "social jet lag."