How does active parental consent influence the findings of drug-use surveys in schools?

This study examines the impact of passive and active parental consent procedures on the type of adolescents participating in a school-based survey examining substance use. Schools recruited from a random sample of metropolitan schools were assigned to passive or active parental consent condition. Results showed that participation rates in active consent schools were lower than in passive consent schools for junior students (60% vs. 80%) but not senior students. Although consent condition had limited impact on prevalence estimates among older students, among younger students estimates of cannabis use and ecstasy use were higher in the passive consent condition than the active consent condition. Active consent procedures introduce some degree of selection bias into studies of adolescents' substance use and may compromise the external validity of prevalence estimates produced, especially among younger students.