We're also seeing an increase in the use of these drugs in young adults.

It is possible that some students know what drugs are and are not included in the tests, and migrate toward using those not included.

Most declines halted this year.

What is significant is that the use of these substances has declined substantially since the recent peak levels reached in the mid-1990s.

There is some logic to that, because if you're buying Ecstasy, you have no idea where it was made or what's in it.

It's the best news we've had to give the country for some years now.