Abstract
The Loeber Risk Score (LRS) was developed to predict early-onset cannabis use in adolescence from late childhood, facilitating early identification. However, the LRS was developed in non-representative historical samples, leaving uncertain its generalizability to children/adolescents across the U.S. today. We externally validated the LRS in a diverse, nationwide cohort (N = 4,898) weighted to the composition of the U.S. Census. Participants in 20 cities completed assessments when youth were approximately 5, 9, and 15 years old. Parents completed the LRS at the age ∼5 and ∼9 interviews. At the age ∼15 interview, youth reported on the onset of alcohol/drug use before age 15, monthly drinking/binge drinking at ages 14-16, and use of cannabis multiple times per month at ages 14-16. First, we validated the LRS measured at age ∼9. Area under the receiver operating curve was 0.62 for onset of cannabis use before age 15, 0.68 for onset of cigarette use before age 15, and 0.62 for use of cannabis multiple times per month at ages 14-16. For drinking outcomes, LRS performance could not be distinguished from chance prediction. The recommended screening cutoff of LRS ≥ 2 identified 24% of children, among whom early-onset cannabis/cigarette use outcomes occurred 1.4-2.2 times more frequently than the general population. The LRS' performance did not vary significantly by sex, race, or ethnicity. When the LRS was measured at age ∼5, AUROC was significantly lower for some outcomes. Together, findings support the LRS measure as a potential tool for identifying children in early or late childhood at risk of early-onset drug use in adolescence.