The THC content in Dutch-grown marijuana has fallen under the 15% for the first time, the Trimbos addiction institute said on Wednesday.

THC is the active ingredient in marijuana and cannabis that creates a high.

Until 2004, the average THC content was above 20%, but this has been falling gradually to between 15% and 18%.

Trimbos analysed marijuana from 48 of the 651 cannabis cafes and found a THC content of 13.5% on average. This is 2% lower than in 2011.

The institute does say, however, that one-third was still well above the 15% limit imposed by the government.

The government announced last year it was planning to classify marijuana with a THC content above 15% as a Class A drug, alongside heroin and cocaine.