The Natural course of cannabis use, abuse and dependence during the first decades of life
Addiction, Volume 103 Issue 3 Page 439-449, March 2008
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1360-0443.2007.02064.x
Axel Perkonigg, Renee D. Goodwin, Agnes Fiedler et al