to rVUS as a function of co-twin’s adolescent-onset cannabis use status. Similarly, even though they did not start using cannabis during adolescence, unexposed members of discordant pairs were somewhat more likely to report rVUS than concordantly never/late-onset users. These results indicated that the presence of an unexposed co-twin marginally reduced the likelihood of rVUS and vice versa. Familial effects were further corroborated by the moderate genetic correlation between adolescent cannabis use and rVUS. However, the upper confidence limit on this correlation estimate did not encompass 1.0 indicating the significant role of specific genetic influences on rVUS that were unrelated to adolescent cannabis use.
