Cannabis products (grass, hashish, pollen, oils, etc.) are extracted from the hemp plant. The most important active substances are THC (tetrahydrocannabinol) and CBD (cannabidiol). THC is responsible for the majority of the psychoactive effects, while CBD has a calming, neuroprotective, antispasmodic and depressant effect. 

Cannabinoid receptor agonists (cannabimimetics), also known as synthetic cannabinoids, are similar to THC in their effect. Cannabimimetics thus mimic the effect of THC. These substances dock at the same places in the brain as THC, but with up to more than 100 times stronger binding, which leads to a significantly more intense effect. 

Risk assessment 

In addition to the known side effects of cannabis, the frequent occurrence of synthetic cannabinoids since the beginning of 2020 means an additional health risk for all users that is difficult to assess. Physical symptoms ranging from nausea, vomiting, sweating, heart palpitations, dizziness and motor difficulties to signs of paralysis or unconsciousness often appeared immediately after consumption. The latter poses the risk of accidents, for example due to falls. Panic attacks, hallucinations or dissociative sensations are mentioned as undesirable psychological side effects. 

For "normal" cannabis, the higher the THC content, the greater the risk of adverse effects. With high-dose cannabis (high THC content), circulatory problems up to circulatory collapse, or anxiety, panic and paranoia can occur. 

When consuming cannabis products ("edibles"), the dosage is even more difficult to assess, making the risks and side effects unpredictable. 

Many of the cannabis samples analysed by DIZ in the first half of 2021 (mainly cannabis flowers containing THC) have a very unbalanced THC-CBD ratio. Most of these samples contained hardly any or only traces of the active ingredient CBD, which has an intoxication-attenuating and neuroprotective effect (protects nerve and brain cells). These cannabis products therefore pose a greater health risk than those containing CBD. Scientific research suggests that cannabis products with an unbalanced THC-CBD ratio (high THC content and low CBD content) pose a higher risk of developing psychoses. 

Cannabis products cannot be visually and/or taste tested for their quality. Synthetic cannabinoids in cannabis products as well as the exact active ingredient contents (potency and THC-CBD ratio) can only be determined by a precise chemical analysis. Furthermore, cannabis products are repeatedly stretched with organic and inorganic products in order to increase profits.

Samples analysed

From January to June 2021, a total of 264 cannabis samples were handed in for analysis at the Drug Information Centre (DIZ) in Zurich. 198 samples were cannabis flowers, 56 samples were hashish and 10 samples were other cannabis products such as oils, liquids and edibles. 

172 of these samples were given without a suspicion of synthetic cannbinoids. They were brought for analysis by the users, who were looking for information on the composition of the substances and the associated risks. Contrary to expectations, synthetic cannabinoids were found in 16 of these samples. 

In the remaining 92 samples, the users suspected that their substance had been mixed with synthetic cannabinoids due to concrete negative experiences. In a total of 21 of these suspicious cases, synthetic cannabinoids could actually be detected. 

Results Active substance content: THC and CBD 

226 samples were analysed in cannabis drug checking for their THC and CBD content. In 38 additional samples, it could only be determined whether the flower or the hashish had been treated with synthetic cannabinoids.

The results regarding THC content are roughly in line with figures from other black market studies, such as the figures published annually by the Swiss Society of Forensic Medicine (SGRM). Data on CBD content in cannabis samples are completely new, as they are not systematically collected in any other context. For this reason, these data are particularly exciting, as for the first time, the long-suspected unbalanced THC/CBD ratio could be proven. Thus, 106 of the tested samples have a CBD content that is below 0.1 %, which also explains the low average CBD content. 

In the following, the THC and CBD values of the flower and hashish samples analysed at the DIZ are given. All samples that showed a CBD type were not taken into account.

  • The average active substance content of the cannabis flowers tested in the DIZ was 13.0 % THC. The active ingredient content of the analysed cannabis flowers varied greatly between 1.7 % and 23.4 % THC. 
  • The average active substance content of the cannabis flowers tested in the DIZ was 0.9 % CBD. The active ingredient content of the analysed cannabis flowers varied greatly and ranged from 0.03 % to 12 % CBD. 
  • The average active substance content of the hashish tested in the DIZ was 20.4 % THC. The active ingredient content of the hashish analysed varied greatly and was between 4.2 % and 49.5 % THC. 
  • The average active substance content of the hashish tested in the DIZ was 4.9 % CBD. The active ingredient content of the hashish analysed varied greatly and was between 0.03 % and 18 % CBD. 

Due to the small number of samples of oils, liquids and edibles, these samples will not be discussed in more detail. 

Graph 1 shows the average THC and CBD content of cannabis samples analysed in the first half of 2021 that were declared as THC samples, broken down into flower and hashish samples, in percentages: 

Average THC/CBD content of analysed cannabis samples with declaration THC flowers, 1st half of 2021, in %, (n=203) 

Graph 2 shows the highest analysed THC value for both the flower and hashish samples in the 1st half of 2021 in percent: 

Highest THC content of all analysed flower and hashish samples with declaration THC in the 1st half of 2021 in %. 

Extenders and impurities 

THC and CBD are naturally occurring cannabinoids in the cannabis plant. Since the beginning of 2020, an increasing number of synthetic cannabinoids have been detected at the DIZ in Zurich. This sudden and frequent occurrence of such samples leads to the assumption that various traffickers have acquired cheap, legal CBD cannabis on a large scale due to overproduction and the associated price collapse, and have added synthetic cannabinoids to it in order to subsequently resell it deceptively as illegal cannabis with a high profit margin. 

It has been known for a long time that cannabis products are sometimes stretched with different substances (e.g. Brix, lead, sand, etc.) in order to optimise profits (more weight). Furthermore, mould can form due to improper drying/storage. These substances are sometimes visually recognisable on the flowers. In the case of sand, a clearly visible layer sometimes forms at the bottom of the storage container. With Brix, a small amount of the bloom can be burnt. Samples mixed with Brix burn very badly, the ash is rather hard and feels greasy and oily when rubbed. Furthermore, fertilisers are often used in cultivation to promote growth, which remain as residues in the plant if not handled properly. Consumption of all these substances poses an increased risk to the health of the consumer. The analysis at the DIZ cannot detect these extender substances. However, apart from fertiliser residues, most extenders are relatively easy to detect by eye or by smell. A detailed list of the most common cannabis extenders can be found on the website of the German Hemp Association.  

In the case of illegally purchased liquids, cases are known in which thickening agents such as vitamin E acetate have been added, which according to a study are extremely harmful to health and have already led to several deaths in the USA. These cases have become known as EVALI(e-cigarette, or vaping, product use associated lung injury). However, no further deaths associated with EVALI have been reported since the publication of this study. Nevertheless, it is recommended to use cannabis drug checking for illegal e-liquids if possible or, if this is not possible, to test cautiously. 

Synthetic cannabinoids and other ingredients in cannabis samples 

In the first half of 2021, 37 samples (14.0 %) of all cannabis samples submitted to the DIZ for analysis were spiked with at least one synthetic cannabinoid. 8 of the samples were spiked with two or more synthetic cannabinoids. 

Of the samples for which a suspicion of synthetic cannabinoids was expressed at the time of distribution, 21 samples (22.8%) actually contained such. Even in samples without suspicion, synthetic cannabinoids were detected in 16 cases (9.3%): Most frequently MDMB-4en-PINACA followed by ADB-BINACA, 5F-MDMB-PICA and 4F-MDMB-BINACA. 

Compared to the previous year, the number of samples tested positive for synthetic cannabinoids has decreased. At the same time, the number of samples submitted as suspected cases remained stable. This is probably related to the fact that last year, among other things through harm-reduction offers as well as the media, a broad education on the topic of synthetic cannabinoids and their effects took place. The consumption of high-dose cannabis products in large quantities leads to undesirable side effects that can easily be confused with the effects of synthetic cannabinoids. Thus, these samples are then given with suspicion of synthetic cannabinoids, although they are high-dose THC cannabis products. 

The results of the analysis are then presented graphically. 

Number of cannabis samples without suspicion of synthetic cannabinoids, 1st half-year 2021 (n=172) 

Graph 4 shows all cannabis samples with suspicion of synthetic cannabinoids in the 1st half of 2021 (n=92): 

Number of cannabis samples with suspected synthetic cannabinoids, 1st half-year 2021 (n=92) 

Graph 5 shows the number of different synthetic cannabinoids according to their frequency on flowers or in hashish in the first half of 2021 (n=45). In this graph, all synthetic cannabinoids are recorded, including samples in which several substances were detected: 

Synthetic cannabinoids analysed by frequency, 1st half-year 2021 (n=45) 


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