It is estimated that minors consume 16% of alcohol beverages sold in the United States (Miller, Levy, Spicer, & Taylor, 2006). The characteristics of the substantial portion of the population who subsequently develop AUD remain to be delineated. In view of the finding that development of AUD at a young age has high heritability (Chen et al., 2011; Cloninger et al., 1981), and evidence pointing to strong genetic correlation between liabilities for different SUDs (Kendler et al., 2007), it was posited that the score on a continuous measure of transmissible risk predicts age at the time of first exposure to alcohol and cannabis. In addition, it was hypothesized that greater transmissible risk is associated with increased likelihood of initiating substance consumption with cannabis. The results confirmed both hypotheses. Each standard deviation unit increase in the TLI is associated with the lowering of age at the time of alcohol initiation by 3.2 months and first cannabis use by 4.6 months. Furthermore, age at the time of first use of alcohol and cannabis mediates the relationship between transmissible risk and both AUD and CUD.
