A new study finds more than 25% of parents of 9- and 10-year-olds say they haven’t made specific rules about substance use for their children, The Hill reports.

The study included almost 12,000 children ages 9 and 10 who were participating in the Adolescent Brain Cognitive Development (ABCD) study. Their parents were asked about availability of and rules about substances. The survey found up to 3% of children say they already have a friend who uses alcohol, tobacco products or marijuana. Those with a friend who has tried one of these substances are much more likely to be curious about trying alcohol or tobacco products.

Up to one-third of the children’s parents say their kids may have easy access to alcohol at home, the survey found.

“The earlier in adolescence a child begins using these substances, the greater the potential impact on brain development and functioning,” lead researcher Meghan Martz of the University of Michigan said in a university news release. “Their household environments and messaging from parents can play a major role at this age, while the influence of peers will become more important over time.”