Furthermore, early users of all three substances were more than twice as likely to meet the criteria for marijuana dependence (21% vs. 8%).
Links
[1] http://www.cesar.umd.edu/cesar/cesarfax/vol23/23-07.pdf
[2] http://www.rethinkpot.org/tags/alcohol
[3] http://www.rethinkpot.org/tags/addiction