The Netherlands Drug Situation 2010 - Trimbos-instituut

analysed. Figure 10.3.4 shows the average concentration of THC in Dutch marihuana(‘nederwiet’), imported marihuana and imported hashish (see also Standard Table 14).Two types of samples of Dutch marihuana were bought: the most “favourite” variety(normally reported here, unless mentioned otherwise) and the most “potent” variety,according to the perception of owners of coffee shops. In 2010 there was a change inlaboratory, which may have had some impact on the trend data (Niesink et al., 2010). Dutch marihuana contains about three times more THC than imported marihuana. Between 2000 and 2004, the percentage of THC in Dutch marihuana increased significantlyfrom 9% to 20%. Between 2005 and 2010 average concentrations fluctuatedbetween 15% and 18%. Since 2001, the annual average concentration of THC in themost favourite variety was not significantly different from that of the most potent variety(17.8% and 17.9% in 2009). The THC concentration in imported marihuana increased between 2007 and 2009 anddropped again in 2010. The percentage of THC in imported hashish dropped from 18.7% in 2006 to 13.3% in2007, and increased thereafter. These changes are hard to explain.Figure 10.3.4:Average THC percentage in cannabis productsSource: THC-monitor, Trimbos Institute (Niesink et al., 2010).The relatively high THC content in Dutch weed compared to imported weed is probablydue to highly professional cultivation methods.As a result of intensified law enforcement in the area of marihuana cultivation (seeprevious National Reports), it might have become more difficult to obtain marihuanawith a good quality standard in Dutch coffee shops. Retail prices have also risen (seesection “Prices” below).THC versus cannabidiol (CBD)The potency of cannabis is generally indicated by the concentration of THC. In recentyears scientific publications increasingly point at the role of another cannabinoid – can-153