Children's Knowledge of Cannabis and Other Substances in States with Different Cannabis Use Regulations.

: Public acceptance of cannabis continues to increase across the US, yet there has been little research on how cannabis legalization affects young children. The present study compared knowledge of cannabis and other substances among children living in states with different cannabis laws and examined whether the association between such substance knowledge and externalizing behavior varies by state cannabis regulations. : Participants were from the Adolescent Brain Cognitive Development Study (ABCD Study®) at the baseline assessment ( = 11,875, ages 9-11, collected from 2016 to 2018). Chi-square difference tests were used to compare nested models testing group differences in knowledge of substances and the association between externalizing disorder/behavior and substance knowledge as a function of state legality of cannabis use (recreational, medical, low THC/CBD, none). : Children living in states with more permissive cannabis laws had a greater knowledge of cannabis and reported more alcohol experimentation. In contrast, knowledge regarding alcohol, tobacco, and other illicit drugs was not greater in children from states with more permissive cannabis laws. Externalizing disorder/behavior was not significantly associated with cannabis knowledge in any group and not significantly different across groups. The association between externalizing disorder/behavior and illicit drug knowledge was significant only in states with the recreational and medical use laws but did not differ significantly across groups. : Children living in environments with more permissive cannabis regulations have greater knowledge of cannabis, but not other substances, and report more experimentation with alcohol.