Science - October 13, 2011

The real dope on cannabis

The cabinet wants to put cannabis containing more than 15 percent THC on the hard drugs list.

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The proposal comes from the Garretsen commission and reflects concerns about the sharp increase in cannabis addiction. The plan has drawn a lot of criticism. Almost all the cannabis grown in the Netherlands (nederwiet) is over the 15 percent mark. So its opponents say the measure is really aimed more at banning cannabis all over again than at protecting public health. A second objection is that it will be impossible to implement. What can the experts tell us about the background to this proposal?
Have THC levels really increased so dramatically in recent years?
The Trimbos Institute has been monitoring the characteristics of cannabis sold in the Netherlands since 1999. In that time the average THC level in nederwiet went from 10 percent to a high of 20 percent in 2004, after which averages stabilized around 16 to 18 percent. There is no reason to assume they will rise any further, says Trimbos Institute researcher Sander Rigter. Imported cannabis still contains around 8 percent THC.
How do Dutch dope growers achieve such high levels?
Breeding cannabis plants is relatively simple, says Evert Jacobsen, professor of Plant Breeding, who has some experience of growing hemp. Because there are male and female plants, you can avoid pollination. So once you have checked the THC levels you can cross-breed your plants selectively. Another reason why the nederwiet is stronger than the imported stuff is that it is fresher and it is grown under controlled conditions. Lastly, there is the sinsimillia method, which involves growing the male and female plants separately so that the THC production in the female plants is not impeded by pollination.
Is dope with more than fifteen percent THC so much more dangerous?
Cannabis use increases the chances of psychological disorders in vulnerable people. Whether its use by healthy people can also lead to schizophrenia is still uncertain. Until a couple of years ago, THC was believed to underlie all the effects of dope, explains Sander Rigter. But it is more subtle than that. The substance known as cannabidiol appears to soften the effects of THC and to reduce anxiety, for example. This makes the ratio between THC and cannabidiol particularly important. Further research should make the relations between these substances clearer. For nederwiet it doesn't make much difference, as the levels of cannibidiol it contains have stayed at 0.2 percent for years.
Is it possible to implement the proposed measures anyway?
In line with the Dutch policy of tolerance, the sale of dope in coffee shops is accepted, but cultivation and wholesale purchase are not. In this ambiguous situation, it is not easy for coffee shops to guarantee the quality of their wares. If a political solution to this problem can be found, then there are few practical objections, according to Robert van Gorcom director of food safety institute Rikilt. His institute is already monitoring the THC levels in hemp. The test can be adjusted and used for dope.
 

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