Marijuana use has been proposed to serve as a “gateway” that increases the likelihood that users will engage in subsequent use of harder and more harmful substances, known as the marijuana gateway hypothesis (MGH). The current study refines and extends the literature on the MGH by testing the hypothesis using rigorous quasi-experimental, propensity score-matching methodology in a nationally representative sample. Using three waves of data from the National Longitudinal Study of Adolescent to Adult Health (1994–2002), eighteen propensity score-matching tests of the marijuana gateway hypothesis were conducted. Six of the eighteen tests were statistically significant; however, only three were substantively meaningful. These three tests found weak effects of frequent marijuana use on illicit drug use but they were also sensitive to hidden bias. Results from this study indicate that marijuana use is not a reliable gateway cause of illicit drug use. As such, prohibition policies are unlikely to reduce illicit drug use.

有人建议使用大麻作为“门户”，以增加用户随后使用更坚硬，更有害的物质的可能性，这被称为“大麻网关假说”（MGH）。本研究通过在全国代表性的样本中使用严格的准实验，倾向得分匹配方法对假设进行检验，从而完善和扩展了有关MGH的文献。使用来自全国青少年到成人健康纵向研究的三波数据（1994-2002年），进行了18个大麻关口假说的倾向得分匹配测试。18个测试中有6个具有统计学意义；但是，只有三个具有实质意义。这三个测试发现频繁使用大麻对非法药物使用的影响较弱，但它们也对隐藏的偏见敏感。这项研究的结果表明，使用大麻并不是非法使用毒品的可靠原因。因此，禁止政策不太可能减少非法药物的使用。