Dear Mr. Dad: A few weeks ago, you wrote about how PTSD after deployment affects spouses in addition to servicemembers themselves. You talked a little about how it affects kids too. But what about families where PTSD isn’t an issue? My brother is in the Army and he and his wife are both being deployed in a few weeks. Their two children, a boy age 11 and a girl age 13, will be staying with my husband and me. How do kids do during the actual time when dad or mom is deployment?

A: The short answer to your question is that most of the more than two million children who have had at least one parent deployed do pretty well. But there’s a significant number that don’t. Children who have a deployed parent (or parents) tend to be more depressed and do worse in school than kids in non-military families—especially if there have been multiple deployments. And a brand new study just found that children with deployed parents are more likely to abuse alcohol, illegal drugs, and prescription medication than non-military kids.

The study was led by Stephan Arndt, Ph.D., a biostatististician at the University of Iowa, and analyzed data from nearly 80,000 students in 6th, 8th, and 11th grades. The team started the project with the hypothesis that a parent’s deployment would increase children’s likelihood of substance abuse. Unfortunately, as Arndt put it, “The numbers suggested we were a lot more right than we wanted to be.” The study was published in the journal Addiction.

Here’s what they found: When looking at alcohol consumption in the previous 30 days, sixth graders with deployed parents were three times more likely to have had at least one drink than non-military kids (12 percent vs. 4 percent) and nearly four times more likely to downed five or more drinks in one sitting (7 percent vs. 2 percent. The difference among 11th graders wasn’t quite as stark: 29 percent of military children binge drank vs. 22 percent of civilian children. But 11th graders with deployed parents were 50 percent more likely to have smoked dope (15 percent vs. 10 percent). And for all grades, military kids were more than twice as likely to have misused prescription drugs (15 percent vs. 7 percent).

One especially interesting thing about this study was that it also compared outcomes for military kids who lived with a parent or other relative (including uncles and aunts like you and your husband) while dad or mom was deployed with those who lived with non-family members during the deployment. And, as you might guess, being forced to live with someone outside the family made things far, far worse. “Deployment is going to be disruptive anyway, which is probably why we see the overall increased risk of substance use in these children. And then for those children where parental deployment means they end up living outside of the family, it’s a double whammy,” Arndt said in a University of Iowa press release. “[T]hat change in these children’s living arrangements grossly affected their risk of binge drinking and marijuana use.”

The best thing you can do is keep a close watch on your niece and nephew. Talk to them about how they’re doing and pay attention to who their friends are. But more importantly, do everything you can to keep them communicating with their parents, whether that’s skype, phone calls, emails, or care packages. The more connected kids feel to their parents during deployment, the less likely they’ll be to get into trouble.