other drug use, abuse, and dependence relative to those who do not use cannabis early (Agrawal, Neale, Prescott, & Kendler, 2004; Lessem et al., 2006; Lynskey et al., 2003; Lynskey, Vink, & Boomsma, 2006). However, only Lynskey et al. (2003) and Agrawal et al. (2004) compared early users not only to both later/never users but also restricted to later users. Replication of this observed association in a variety of samples is required, as it is possible that associations may vary across age, birth cohort, and/or culture.
