by KYW’s medical editor Dr. Brian McDonough

Starting school just a half-hour later may make teens cheerier and more motivated according to researchers at the University of Rhode Island.

You may not be aware of this but the average adolescent needs nine hours of sleep each day. We all have an internal clock that determines our sleep and wake cycle. Adolescents undergo substantial shifts in their circadian rhythms, which make it easier for them to stay up late and harder for them to wake up early. Getting up early for school actually works against this cycle.

The question needs to be asked, should school be starting later. Of the high school students tested, nearly two-thirds of students said they were at least somewhat unhappy or depressed before the start time change, 45 percent said so afterwards, while the percentage of students who said they felt irritated or annoyed dropped from 84 percent to 63 percent.

The report is in The Archives of Pediatric and Adolescent Medicine.