Variation in Youthful Risks of Progression From Alcohol and Tobacco to Marijuana and to Hard Drugs Across Generations

Authors: Golub, A., Johnson, B.D.
You will find this study mentioned in the comments section related to "gateway" status of cannabis in the blog post:

Alcohol, Weed and Recovery. Although the authors suggest that no up-tick could be found to suggest that cannabis functions as a gateway drug, later National Household Surveys on Drug Abuse confirmed the up-tick was present.