Teenagers who get less sleep are more likely to engage in a wide range of risky activities, including some with terrible consequences for those around them. If we can look past blaming just smartphones, it appears some of the things imposed on adolescents may also be encouraging juvenile delinquency.

Dr Michelle Short of Flinders University has conducted a meta-review of 24 studies comparing sleep patterns and various risk-taking behaviors in more than 500,000 adolescents. The studies varied in quality, but the results were remarkably consistent.

Teenagers who are not getting enough sleep are almost 50 percent more likely to engage in alcohol and drug use, violence, unsafe sex, and risky behavior on the road than those who are sleeping soundly, Short reported in Sleep Medicine Reviews. “The only thing where we didn't find a correlation for was gambling,” Short told IFLScience.

Short admitted that the studies she analyzed don't test causality. “It could be that there is a third variable, such as parental involvement and limit setting,” she said. However, she noted other studies have tested the same individuals' behavior when sleep-deprived and well rested. “They couldn't test for violence or underage drinking,” she noted, but when adolescents played virtual reality games or drove on racing tracks, those without sufficient sleep took more risks. If, Short noted, this occurs even on a short-term basis, the effect is likely to be greater over time. The majority of American teens get insufficient sleep on weeknights.

“If future research can garner stronger evidence that sleep plays a role in risk-taking, then intervention campaigns promoting road safety, drug and alcohol use will profit from targeting sleep as a means of harm minimization or reduction,” Short said in an emailed statement.

However, simply running promotional campaigns on the benefits of a good night's sleep may not be the answer. “We know from studies of school-based interventions that teenagers can learn about sleep and understand why they need it, but it almost never translates to getting more sleep,” Short told IFLScience.

Instead, what has proven successful is having schools start classes later, avoiding activities prior to the official start time, and moderating homework allocations. Short noted that in her native Australia, guidelines oppose school classes or compulsory sporting activities before 8:30 but are frequently ignored.

The problem is worse in schools where many students have long journeys or where homework loads are frequently heavy. All these activities are frequently promoted as building discipline and character, but they may be having the opposite effect.

Earlier this month, another study confirmed reduced sleep in adults worsens cardiovascular disease. Just days ago, sleep deprivation was tied to a second protein thought to cause Alzheimer's disease and increase sensitivity to pain.