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THC content of cannabis/marijuana in The Netherlands.

Trimbos Institute, Netherlands


THC content of cannabis/marijuana in The Netherlands.



Since the 1970’s cannabis policy in The Netherlands has been different from that in many

other countries. It is based on the idea that separating the markets for hard and soft

drugs prevents cannabis users to resort to hard drug use. Therefore, so called Coffee

shops emerged where the selling and the use of cannabis are not prosecuted, provided

certain conditions are met. The number of coffee shops has been declining steadily from

almost 900 at the start of this millennium to 567 in 2017 (see figure 1.8). It is up to the

local authorities to decide about the presence of coffee shops within the municipality.

About 25% of the municipalities have one or more coffee shops.

Nowadays, many of the cannabis products sold in these coffee shops originate from

Dutch-grown grass called “nederwiet”. It is estimated that over 80% of the

cannabisproducts sold in the coffee shops is Dutch-grown grass and the rest of the sales

is mostly hash (mostly imported from Maroc). On behalf of the Ministry of Health,

Welfare and Sports we investigate the potency of cannabis products as sold in coffee

shops. This study has been done annually since the winter of 1999-2000.

9-Tetrahydrocannabinol (THC) is the main psychoactive compound in marihuana (herbal

cannabis) and hashish. The aim of this study is to investigate possible changes in the

concentration of THC in marihuana and hash (=cannabis resin) as sold in Dutch coffee

shops. In addition we examined whether there are differences between the cannabis

products originating from Dutch grown hemp (nederwiet) and those derived from

imported hemp. This is the eighteenth consecutive year that this study has been

performed. Besides THC, the content of two other cannabinoids, cannabidiol (CBD) and

cannabinol (CBN), are measured.

The names and addresses of 50 (out of a total of 567) Dutch coffee shops were randomly

selected. For the purpose of this study, 63 samples of nederwiet, 10 samples of imported

marihuana, 21 samples of Dutch hash and 56 imported hash samples were anonymously

bought in 50 of the selected coffee shops. In addition, 50 samples of the most potent

(herbal) marihuana product available were bought. As a rule samples of 1 gram were


Traditionally hash contains more THC than marihuana and homegrown products mostly

cultivated indoors contain more THC then imported products cultivated outdoors.

Imported hash contained more THC on average than imported marihuana (20,8% versus

6,9% in 2017) and Dutch hash contained more THC on average then Dutch marihuana

(35,1% versus 16,9% in 2017). This year the most potent marihuana product contained

more THC on average than the most popular (18,7% versus 16,9%; p < 0,05).

Consumers do however prefer the more potent indoor cultivated marihuana. Nederwiet is

estimated to comprise around 80% of all sales in coffees shops, while imported hash

comprises around 20%.

All the different cannabisproducts were not significantly stronger than in 2016. For the

most popular and most potent homegrown marihuana and the imported hash there has

however been an increase in THC content compared to the years before. The average


THC content of the most popular and most potent homegrown marihuana increased till

2004, after that there was a steady decline till 2013 and 2014 respectively, and since

then it increased again (13,5% in 2013 vs 16,9% in 2017 for the most popular varieties

and 15,3% in 2014 versus 18,9% in 2017 for the most potent varieties). The average

THC content of imported hash has also increased since 2014 (from 14,9% in 2014 to

20,8% in 2017) and has never been as high as this year. A switch to other plants in the

Rif-area in Maroc in recent years has probably been the cause of this.

There is some evidence that not only the THC-content is indicative for the effects and

risks of cannabis, but that CBD might attenuate some of the negative effects of THC

(Niesink & Van Laar, 2013). This means that cannabis with a high CBD/THC ratio would

have less negative health consequences than cannabis that has little or no CBD.

Nederwiet has very low levels of CBD (median = 0,3%), whereas imported hash

contained on average 8,4% CBD.

Because CBN is a degradation product of THC, the ratio between CBN and THC can give

an indication of the freshness of the preparation (Ross and Elsohly, 1997). Levels of CBN

were higher in imported marihuana and hash compared to products derived from

homegrown cannabis. Also the ratio of CBN/THC was significantly higher in the imported

products. The ratio was higher in imported marihuana compared to nederwiet and in

imported hashish as compared to hashish made from nederwiet.

Prices that had to be paid for imported marihuana were lower than those for any of the

other cannabis products; the prices of hash made from nederwiet were higher. The

average price for nederwiet was €10,11 per gram, for a gram of imported marihuana

€4,84. The average price for a gram of imported cannabis resin was € 9,93 and for a

gram of Dutch resin €23,04.


All reports of this monitor are downloadable as PDF via www.trimbos.nl. If you have any

questions please sent an e-mail to srigter@trimbos.nl.