Allowing a kid under age nine to walk around tired all day or not helping him get regular sleep at night may increase the likelihood that he’ll experience drug and alcohol issues as a teenager, according to a recent study.

Lead author Maria M. Wong, PhD, a psychology professor at Idaho State University, spent years examining the effect of lack of rest on 386 children ages three to eight. Over time, a link became evident: Kids who were often exhausted had a tendency to develop trouble with self-restraint in adolescence and then to end up struggling with alcohol. “By age 18 to 20, overtired children were twice as likely as their peers to binge-drink, experience alcohol-related blackouts and drive under the influence,” she says.

The research does not prove that sleep deprivation causes substance problems. Still, it does suggest that childhood exhaustion has a dele-terious effect on the emerging ability to restrain oneself. Kids ages three to eight need 10 to 13 hours of sleep per night, according to the National Sleep Foundation. Create a restful atmosphere by establishing sleepy-time traditions, saying good-night and waking kids up at the same time every day and prohibiting stimulants (TV, video games, sugary foods) a few hours before bed. Also, model healthy behavior. “If we don’t value our sleep, our kids will have a hard time learning to do otherwise,” says Wong. For more info, go to sleepfoundation.org.