THC Content of Cannabis in Netherlands.

The policy on cannabis use in The Netherlands is substantially different from that in many other
countries. It is based on the idea that separating the markets for hard drugs and soft drugs prevents soft drug users to resort to hard drug use. Over the years so-called coffeeshops emerged.

Coffeeshops are alcohol free establishments where the selling and using of soft drugs is not prosecuted,provided certain conditions are met. Many of the cannabis products sold in these coffeeshops originate from Dutch-grown grass called ‘nederwiet’. Critics of the Dutch drug policy have claimed that the THC-content of nederwiet has increased drastically over the last decades.

However,the THC-content of cannabis products as sold in coffeeshops has not systematically been
tested. On request of the Ministries of Health and Justice, the potency of cannabis products as sold in coffeeshops in The Netherlands has been investigated since 1999.

Tetrahydrocannabinol (THC) is the main psychoactive compound in marihuana and hashish. The
aim of this study was to investigate the concentration of THC in marihuana and hash as sold in
Dutch coffeeshops. In addition we wanted to know whether there are differences between the cannabis products originating from Dutch grown hemp (nederwiet) and those derived from imported hemp. It is the eighth time that this study has been performed.

It might be that there are differences in potency of cannabis products in different seasons of the
year. For that reason, since 2001, every year extra samplings have been done in September. In
these extra studies only nederwiet was bought. The names and addresses of 50 Dutch coffeeshops were randomly selected. For the purpose of this study, 53 samples of nederwiet, 24 samples of foreign marihuana, 14 samples of Dutch hash and 42 samples of hash prepared from foreign hemp were anonymously bought in the selected coffeeshops.

In addition, 47 samples of the most potent marihuana product available in the coffeeshop,
were bought. As a rule samples of 1 gram were bought. The average THC-content of all the marihuana samples together13 was 14,2% and that of the hash-samples 17,2%. The average THC-content of nederwiet (16,0%) was significantly higher than that of foreign marihuana (6,0%). Hash derived from Dutch hemp contained more THC (29,1%) than hash originating from foreign hemp (13,3%). The average THC percentage of nederwiet was significantly lower than last year (16,9 vs. 17.5%).

Again, the THC-percentage in foreign marihuana did not differ from the previous samplings. The average THC-percentage of the marihuana samples that were bought as most potent (16,5%) did not differ from the average percentage of nederwiet. The potency of nederwiet bought in September 2006 was not significantly different from samples bought in December/January 2007. It was the first time that no seasonal influence in THC-levels was found. There seems to be a stabilization of the potency of nederwiet. Such stabilization was first seen in the cannabis samples bought in September. Most potent as indicated by the coffeeshop personnel. This is not corrected for in terms of relative contribution of number of foreign or Dutch samples.

Prices that had to be paid for foreign marihuana were lower than those for any of the other
cannabis products. The prices of nederwiet increased significantly the last year.
The most notable finding in the current investigation was a significant decrease in the potency
of imported hash (from 18,7% in 2006 to 13,3% in 2007). Climate factors in the countries
of origin seem to be the most logical explanation. Future monitoring has to show
whether this is an incident or a trend.

Source:THC-concentration in weed, netherweed and hasj in the Dutch coffeeshops (2006-2007)’, English summary.Trimbos Institute

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