THC concentrations in marihuana products sold in Dutch coffeeshops

contact address:

Trimbos Institute: Netherlands Institute of Mental Health and Addiction
PO Box 725

3500 AS Utrecht

Tel.: (030) 297 11 00


Dr. R.J.M. Niesink.

Goal of the study:

To investigate the concentration of delta-9-tetrahydrocannabinol (THC) in marihuana and hash as sold in Dutch coffeeshops. In addition it is studied whether there are differences between the cannabis products originating from Dutch grown hemp (nederwiet) and those derived from foreign hemp.

Type of study:

Field investigation.



Coffeeshops in The Netherlands.

Design and

Every year, 50 coffeeshops are randomly selected. For the purpose of the study, samples of nederwiet, foreign marihuana, Dutch hash and foreign hash are anonymously bought in the selected coffeeshops. After the transaction a number of questions about the samples are asked to the shop keeper. THC concentrations are chemically analysed in a specialized laboratory.


December 1999.




The Ministry of Health, Welfare and Sport (VWS)


Delta laboratory

PO Box 800

3170 DZ Poortugaal


The Ministry of Health, Welfare and Sport (VWS) and the Ministry of Justice.


The average THC content of the marihuana samples in 1999 was 7.5% and that of the hash-samples 12.6%. The average THC content of nederwiet (8.6%) was significantly higher than that of foreign marihuana (5.0%). Hash derived from Dutch hemp contained more THC (20.7%) than hash originating from foreign hemp (11.0%). These THC percentages do not deviate much from the percentages that have been reported by the Dutch Forensic Institute in the middle of the nineties about confiscated marihuana and hash samples. The prices that had to be paid for nederwiet and Dutch hash were higher than the prices for foreign marihuana and hash. The price for nederwiet in Amsterdam was higher than in the rest of the country. There is a significant correlation between price and THC content of the cannabis products.

When the THC concentrations in nederwiet are compared with the THC concentrations in marihuana from foreign studies it must be concluded that the concentrations in nederwiet are nothing out of the way. The THC-content of nederwiet is comparable with the THC content of sinsemilla samples as measured in the US between 1980 and 1997.


Yearly report.


Niesink, R.J.M. (2000) THC-concentraties in wiet, nederwiet en hasj in Nederlandse coffeeshops. Utrecht, Trimbos-institute.


Project is part of the program Epidemiology and Monitoring of Addiction of the Trimbos institute.

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