IN a large national survey of cannabis users in Japan, researchers found little evidence to support the long-standing “gateway drug” hypothesis, a theory suggesting that cannabis use leads to subsequent consumption of more harmful substances such as methamphetamine or other illicit drugs.
The secondary analysis included responses from 3900 individuals with a history of cannabis use. Participants, primarily male and aged 20–24, were recruited online and asked to report on their lifetime use of cannabis, alcohol, tobacco, and other substances. The researchers focused on the order of drug initiation and the likelihood of progressing to other substances after cannabis use.
Findings indicate that cannabis was typically the third substance used, after tobacco and alcohol. The odds of initiating other substances following cannabis use were low. Specifically, the odds ratios for subsequent use of alcohol, tobacco, methamphetamine, and other illicit drugs were 1.25, 0.77, 0.08, and 0.78, respectively. Notably, nearly 50% of participants who listed cannabis as their third substance did not report advancing to any other drug.
These results contrast sharply with prevailing assumptions in Japanese drug policy, where cannabis is often portrayed as a stepping stone to more dangerous drug behavior. Instead, the study suggests a different dynamic, one in which cannabis use follows more socially accepted substances like alcohol and tobacco, and rarely progresses to harder drugs.
The authors propose that shared psychosocial vulnerabilities, rather than a pharmacologic gateway effect, may better explain patterns of drug use in this population. Additionally, Japan’s strict drug regulations and social stigmas may influence usage behaviors differently than in Western contexts.
While the study is based on self-reported data and limited to individuals with internet access, it nonetheless raises important questions about how cannabis is perceived and policed in Japan. The authors call for further research to assess how policy changes and legalization trends could impact future drug use patterns both locally and globally.
Reference:
Masataka Y et al. Revisiting the Gateway Drug Hypothesis for Cannabis: A Secondary Analysis of a Nationwide Survey Among Community Users in Japan. Neuropsychopharmacol Rep. 2025;45(3):e70033.
