Anyone who’s been a teenager or knows one has seen it: teenagers like to sleep in, and they need a lot of sleep. Research is now showing that this is a cross-cultural, biological reality for adolescents. And so the benefits are starting to pile up for schools that are accommodating this biological reality by starting later.

Otherwise, as Kyla Wahlstrom of the University of Minnesota writes, we put these teens at risk:

Studies on sleep in general, and on sleep in teens in particular, have revealed the serious negative consequences of lack of adequate sleep. Teens who are sleep-deprived – defined as obtaining less than eight hours per night – are significantly more likely to use cigarettes, drugs and alcohol.

The incidence of depression among teens significantly rises with less than nine hours of sleep. Feelings of sadness and hopelessness increase from 19 percent up to nearly 52 percent in teens who sleep four hours or less per night.

Teen car crashes, the primary cause of death for teenagers, are found to significantly decline when teens obtain more than eight hours of sleep per night.

It’s been very encouraging though to see the impacts on teen health from schools that are starting later in the morning:

Results from schools that switched to a later start time are encouraging. Not only does the teens’ use of drugs, cigarettes and alcohol decline, but their academic performance also improves significantly with later start time.

The Edina (Minnesota) School District superintendent and school board was the first district in the country to make the change. The decision was a result of a recommendation from the Minnesota Medical Association in 1996.

Research showed significant benefits for teens from that school as well as others with later start times.

For example, the crash rate for teens in Jackson Hole, Wyoming, in 2013 dropped by 70 percent in the first year after the district adopted a later high school start.

It’s promising stuff. Hopefully this practice will become the norm across the country.