Adolescents who do not get enough sleep are more at risk for alcohol and marijuana use, conclude the results of research published this month in the Journal of Adolescent Health. This study joins another, also published this month in the journal Sleep Medicine, showing that adolescents who do not get enough sleep are more at risk for anxiety disorders, and a similar 2014 journal Sleep study showing that sleep-deprived teens are at greater risk for depression.
Researchers and health professionals have long known that too little sleep in adolescence is related to pretty much all things bad for their mental health, including irritability, moodiness, anxiety, poor decision-making, inattention, behavior problems, and even suicide ideation and attempts.
But with most prior teen sleep research, there's been a chicken-and-egg, which-came-first dilemma: Does lack of sleep cause all that teen misery? Or does the misery cause all those teen sleep problems?
That's why the three studies mentioned above are important: they are among the first to follow large groups of teens over time – four years in the case of the substance use study and one year in the case of the anxiety and depression studies – which allowed them to answer the question of what causes what.
In all three studies, the answer was clear. Insufficient sleep came first and predicted increased risk for alcohol or marijuana use, anxiety, and depression, not the other way around. Only in the depression study did authors also find what's known as a reciprocal relationship in that existing depression predicted later sleep problems, which authors interpreted as sleep deprivation contributing to development of depression, which in turn predicts poorer sleep.
Taken together, these results suggest a clear pathway to preventing teen mental health problems and improving their happiness, functioning, and quality of life: Focus on their sleep, specifically making sure they get enough of it.
This is harder than it sounds. Ask any parent or any teacher. Adolescents need about nine hours of sleep a night to function optimally, and the vast majority of American teens do not get that amount, particularly on weeknights. Research from the National Sleep Foundation has shown that about 59 percent of middle schoolers and 87 percent of high school students do not get the recommended nine hours they need, with about 20 percent of teens reporting they get less than six hours a night!
The major cause of this epidemic of teen sleep deprivation is not, as you might initially guess, excessive use of electronic devices. Rather it is the unhappy result of a natural, unavoidable shift in brain function that occurs in adolescence combined with earlier school start times from middle school onward.
It's a little-known fact that one of the many physical changes of adolescence is a shifted circadian sleep clock, making it physically very hard for teen brains to fall asleep before 11 pm or wake up before 8 a.m. Circadian clocks shift back in adulthood, which is why most adult brains are pretty comfortable with seven to eight hours of sleep and 6 a.m. wake-up times.
That adolescent brains physically need to sleep later than children or adults prompted the American Academy of Pediatrics to release an impassioned policy statement in 2014 recommending that no middle or high school start earlier than 8:30. Other than for a few districts here and there, however, this science-backed plea has not been heeded; nationally, only 15 percent of public high schools start at 8:30 or later.
Hence we have a nation of chronically sleep-deprived teens and it is a national scandal. The National Sleep Foundation website has a list of recommendations for promoting good sleep habits that are very worth following. But until school start times are delayed so that teens are afforded the basic human right to obtain the amount of sleep they need, we will continue to have a lot of teen misery on our hands. And on our conscience.