Youngsters whose parents or siblings have been deployed are more likely than their peers to use alcohol and drugs, says a new study.

The study included 14,000 children who were between grades 5 and 11. The participants were enrolled in the 2011 California Healthy Kids Survey. The survey asked the children if their parents or siblings were in the military and if they (the children) had used alcohol or drugs in the past 30 days.

Study results showed that youth, whose parents or siblings were deployed, were at 14 percent higher risk of abusing drugs than other people. Researchers found that military deployment of parents or siblings increased both recent and lifetime use of drugs, but not smoking.

"Everyone talks about the impact of parents, but no one talks about the impact of other close family members, such as siblings. There is research to suggest that the deployment of a sibling is similarly disruptive as parental deployment. Parental concern may influence their interactions with the younger sibling who is left to cope with their own sense of loss as well as their parents'," said Tamika Gilreath, Ph.D., from University of Southern California's School of Social Work, lead author of the study.

More than 2 million children in the U.S. have been affected by military deployment of their parents. These children are at a high risk of suffering from behavioral problems, sleeping disorders and higher stress. These children are also likely to suffer from declining grades and child maltreatment, according to a related study that was focused on psychiatric influence of military deployment of a parent.

"This study is timely because recently, there has been greater focus on the effects of deployment on veterans and their families and this focus has stimulated data collection among this population so that we can better understand the issues," said Randi Alter, Ph.D., of the Indiana Prevention Resource Center at Indiana University School of Public Health, Bloomington, who was not involved in the study, according to a press release.

Researchers recommended that schools that have a high density of students whose parents are deployed overseas must include education on substance use in their curricula.

The study is published in the American Journal of Preventive Health.