A study published this week in Forensic Science International used wastewater testing to track the prevalence of cannabis and CBD use in Japan between 2020 and 2023.
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Researchers from The University of Queensland and Kanazawa University found that the “prevalence of THC use remained low in Japan compared to other countries despite a steady increase in recent years, but the use of CBD was much more common than in other countries.”
The study analyzed samples from a wastewater treatment plant serving roughly 120,000 people on Honshu Island. Biomarkers for THC and CBD were detected in most samples, with THC indicating an average consumption of about 5 doses per 1,000 people per day. Cannabis use rose steadily, increasing roughly 27% each year during the study period. However, even with that growth, the per capita level of THC detected was up to 100 times lower than in North America.
CBD, which is legal in Japan for medical purposes, showed a far stronger presence. Researchers determined that most CBD measured in wastewater originated from direct consumption of CBD products rather than trace amounts in cannabis. They concluded that CBD use in Japan was as common—or more common—than THC use, making it more prevalent compared to patterns seen in other countries.
The authors noted that Japan maintains some of the world’s strictest cannabis laws, including penalties of up to seven years in prison for nonmedical use. Despite this, the findings suggest cannabis consumption is gradually increasing. At the same time, the study highlights the unique role of CBD in Japan, where it is more widely accepted and used than in many other parts of the world.
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