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Is Cannabis a Gateway Drug? Key Findings and Literature Review

NCJ Number
Date Published
November 2018
96 pages
This report presents the findings and methodology of a literature review of research relevant to an evaluation of the validity of the "gateway" hypothesis that using cannabis causes the user to progress to the use of harder illicit drugs such as cocaine or heroin.
This literature review analyzed 23 peer-reviewed research studies, both human-based and animal-based, that focused on cannabis use and its link with the subsequent use of other illicit drugs. Overall, the literature review concludes that existing statistical research and analysis relevant to the "gateway" hypothesis has produced mixed results, thus failing to provide clear scientific support for cannabis use as an inevitable "gateway" to harder illicit drug use. This necessitates the main conclusion that "no causal link between cannabis use and the use of other illicit drugs can be claimed at this time." This report notes that the current state of research on this issue is limited, and the studies that have been conducted suffer from difficulties in collecting information and applying the findings to a larger population. The report further notes that although many of the reviewed studies found statistically significant associations between cannabis use and the users' later use of other illicit drugs, there is currently no conclusive evidence that cannabis use caused the later use of harder illicit drugs. Recommendations for future research advise that an analysis of cannabis and its association with other illegal substances should be conducted with a design that randomly assigns selected human participants to control groups and experimental groups, and that potential participants be screened for confounding variables, such as genetic predispositions to addiction. 14 tables, 5 figures, a 59-item bibliography, and appended details on study design

Date Published: November 1, 2018