Masataka Yuji, Katayama Munenori, Umemura Futaba, Sugiyama Takeshi, Miki Naoko, Akahoshi Yoshiyuki, Oka Chihiro, Asahi Takashi, Matsumori Takashi, Takumi Ichiro, Murata Hidetoshi, Matsumoto Toshihiko
Department of Neurosurgery, St. Marianna University School of Medicine, Kawasaki, Japan.
General Incorporated Association Green Zone Japan, Saitama, Japan.
Neuropsychopharmacol Rep. 2025 Sep;45(3):e70033. doi: 10.1002/npr2.70033.
Cannabis has historically been used for medicinal and industrial purposes, but is strictly regulated worldwide due to the psychoactive effects of THC. In Japan, cannabis is frequently labeled a "gateway drug," yet strong causal evidence for progression to other substances is limited. This study investigates whether cannabis acts as a gateway drug among Japanese users.
An anonymous online survey was conducted in January 2021 with 3900 individuals reporting lifetime cannabis use in Japan. Participants were recruited via social media. The survey gathered data on demographics, cannabis and other substance use history, order of substance initiation, psychiatric background, and criminal records. A Sankey diagram visualized substance use progression, and odds ratios were calculated to assess the likelihood of using other substances following cannabis use.
Of all respondents, 81.5% were male, with the largest age group being 20-24. Tobacco and alcohol were the most common initial substances, while cannabis was typically the third. Odds for subsequent use of alcohol, tobacco, methamphetamine, and other illicit drugs after cannabis use were 1.25, 0.77, 0.08, and 0.78, respectively, suggesting low probabilities of progression. Nearly half of those who reported cannabis as their third drug did not use other substances afterward.
Cannabis use in Japan typically follows alcohol and tobacco, and rarely leads to further drug use. These findings challenge the gateway hypothesis in the Japanese context. Shared vulnerabilities and strict drug policies may shape these patterns. Further research is warranted to explore the impact of legal changes on drug use behavior.
REGISTRY AND REGISTRATION NUMBER OF THE STUDY/TRIAL: Not applicable.
大麻在历史上一直被用于医疗和工业用途，但由于四氢大麻酚的精神活性作用，在全球范围内受到严格管制。在日本，大麻经常被贴上“入门毒品”的标签，但关于其发展为其他毒品的有力因果证据有限。本研究调查大麻在日本使用者中是否起到入门毒品的作用。
2021年1月对3900名报告在日本有过终生大麻使用经历的个人进行了一项匿名在线调查。参与者通过社交媒体招募。该调查收集了有关人口统计学、大麻及其他毒品使用史、毒品使用起始顺序、精神病史和犯罪记录的数据。用桑基图直观展示毒品使用进展情况，并计算优势比以评估在使用大麻后使用其他毒品的可能性。
在所有受访者中，81.5%为男性，最大年龄组为20 - 24岁。烟草和酒精是最常见的起始使用毒品，而大麻通常是第三种。在使用大麻后随后使用酒精、烟草、甲基苯丙胺和其他非法毒品的优势比分别为1.25、0.77、0.08和0.78，表明发展为其他毒品的可能性较低。将近一半将大麻作为第三种使用毒品的人之后未使用其他毒品。
在日本，大麻使用通常发生在使用酒精和烟草之后，且很少导致进一步的毒品使用。这些发现对日本背景下的入门毒品假说提出了挑战。共同的易感性和严格的毒品政策可能塑造了这些模式。有必要进行进一步研究以探讨法律变化对毒品使用行为的影响。
研究/试验的注册机构和注册号：不适用。
