A new review of recent research has found that starting school later has a positive impact on teenagers, including longer sleep duration and a reduced number of car accidents.

Carried out by a team of representatives from the American Academy of Sleep Medicine, Centers for Disease Control and Prevention, Sleep Research Society, and American Academy of Dental Sleep Medicine, the review looked at 18 peer-reviewed studies published before April 2016 as part of the National Healthy Sleep Awareness Project.

The findings, which are published in the Journal of Clinical Sleep Medicine, showed that starting high school later in the morning was associated with various positive outcomes among teenagers.

When school started up to 60 minutes later, students slept for an extra 19 minutes a night during the week, and when school started more than 60 minutes later students gained around 53 minutes of extra sleep a night.

Starting school later was also associated with a reduction in car accident rates, less subjective daytime sleepiness, and lower differences between sleep durations on school and weekend nights.

The review also found a possible link between a later school time and a decrease in lateness or truancy, and a possible positive association with better behavioral health.

However the results showed mixed results for a link between later school times and an improvement in grades or standardized test scores.

Commenting on the findings lead author Timothy I. Morgenthaler said, "Many people believe that school start times are one of the big reasons students do not get enough sleep; a CDC study found that 85.6 percent of U.S. high schools started before 8:30 am, which is the earliest time recommended by the American Academy of Pediatrics. Because of this, there is a push to move school start times later."

"Our nation's future is literally dependent upon the physical, mental, and educational excellence of our high school students," he continued, "The most recent national surveys show that less than one third of high school students get enough sleep as recommended by the leading national authorities. This is of concern since inadequate sleep has been linked to worsened mental health, decreased ability to learn, increased obesity rates, increased motor vehicle accidents, and even increased substance abuse."

For optimal health the American Academy of Sleep Medicine recommends that adolescents between the ages of 13 and 18 years should sleep 8 to 10 hours per 24 hours on a regular basis, although data suggests around 69 percent of high school students achieve less than 8 hours sleep on a school night.

The American Academy of Sleep Medicine also state that due to a natural shift in the timing of the body's internal "circadian" clock during puberty, most teens have a biological preference for a late bedtime, which does not suit the current early school start times.