Polygenic Risk for Substance Use Disorders as Predictors of Substance Use Initiation Among African American Youth.

Objective: Despite adverse health consequences associated with early substance use initiation, less is known about the influence of genetic risk on initiation and environmental characteristics that may moderate these associations, particularly among African Americans. We examined whether genetic risk for alcohol use disorder, cannabis use disorder, and nicotine dependence is associated with age at initiation of these substances and whether community disadvantage and parental monitoring moderate these associations in a sample of African American youth.

Method: Participants (n = 1,017; 56% female) were initially recruited for an elementary school-based universal prevention intervention trial. At about age 20, participants reported on their age at initiation of alcohol, tobacco, and cannabis use and provided a saliva or blood sample. At about age 12, caregiver reports on parental monitoring were obtained, along with census-tract data to measure community disadvantage. Hypotheses were tested using Cox Proportional Hazard Models.

Results: Higher alcohol use disorder polygenic risk scores (PRSs) were associated with later alcohol initiation (hazard ratio = 0.78, 95% CI [0.65, 0.94]). Cannabis use disorder and nicotine dependence PRSs were not associated with initiation of these substances. We observed an interaction between the cannabis use disorder PRS and parental monitoring; among individuals with high cannabis use disorder PRS, high monitoring was associated with earlier cannabis initiation, whereas among individuals with low PRS, low monitoring was associated with earlier initiation.

Conclusions: Findings largely indicate that PRSs for substance use disorders are not associated with age at initiation among African American youth. Parental monitoring may influence the association between cannabis use disorder PRS and age at cannabis initiation, but replication of our findings is warranted.