In 2025, a total of 373 cannabis samples were submitted for analysis at the Drug Information Center (DIZ) in Zurich. Of these, 195 were cannabis flowers, 136 were hashish, and 45 were other cannabis products such as oils, liquids, edibles, and dabs (cannabis concentrate).
Synthetic cannabinoids
In 2025, 15 (4.0%) of all cannabis samples submitted to the DIZ for analysis were adulterated with at least one synthetic cannabinoid. In 2024, 15 (3.6%) and in 2023, 19 (4.7%) of all cannabis samples submitted to the DIZ for analysis were adulterated with at least one synthetic cannabinoid.
Semi-synthetic cannabinoids
In 2025, 30 samples containing delta-8 and one sample containing HHC were tested at the DIZ.Delta-8-THC, if present at all, occurs only in very small amounts as a natural cannabinoid in the hemp plant. However, since a strikingly high concentration of∆8-THC was detected in some samples, there is suspicion that it was added to CBD flowers through non-natural means or applied subsequently. This suspicion is reinforced by the frequently high CBD levels measured at the same time.
The detailed 2025 cannabis analysis can be found in the attached report. These are the key findings from 2025:
– The number of samples analyzed—373—was slightly lower than in previous years.
– Cannabis in flower form still contains very low levels of CBD. Since CBD is believed to have a protective effect (reducing the adverse effects of THC), this is problematic from a harm reduction perspective. It is recommended, especially for cannabis with very high THC content, to mix it with CBD-rich cannabis.
– The average THC content in the samples has been rising slightly year after year.
– Once again, there was an increase in the number of samples containing semi-synthetic cannabinoids (∆8-THC and HHC). A total of 31 cases were recorded.
– In recent years, there has been a steady increase in alternative forms of cannabis use (dabs, vapes, etc.) in drug testing. This year, samples that were not hashish or flower accounted for just under 12.1% of the total.
– The number of suspected cases involving synthetic cannabinoids is declining, and users’ assessments are also proving to be more accurate. In 2022, 90 samples were submitted as suspected cases; in 2023, the number was 64; and this year, it was 73. There has been a marked increase in the number of confirmed suspected cases. In 2022, only 5.5% of suspected cases were confirmed. In 2023, the figure was as high as 23.4%. Last year, this high rate dropped slightly to just under 11%, and in 2025 it remained in a similar range at 9.6%. This suggests that, on the one hand, consumers are aware of the possibility of contamination and, on the other hand, are better able to identify the symptoms of synthetic cannabinoids. However, it also indicates that the contaminated samples are sometimes difficult to distinguish from very potent cannabis.
– Compliance with the safe-use guidelines remains very important in this dynamic cannabis market.
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The results published here are not representative of the substance market in the city of Zurich.
