Trevor Butterworth does some excellent hype-busting of a "reefer madness" campaign in the Brit tabloids. Quoting a reseacher from the Guardian:
"There is exceptionally strong cannabis to be found in some parts of the UK market today: but there always has been. The UN Drug Control Programme has detailed vintage data for the UK online. In 1975 the LGC analysed 50 seized samples of herbal cannabis: 10 were from Thailand, with an average potency of 7.8%, the highest 17%. In 1975 they analysed 11 samples of seized resin, six from Morocco, average strength 9%, with a range from 4% to 16%.
To get their scare figure, the Independent compared the worst cannabis from the past with the best cannabis of today. But you could have cooked the books the same way 30 years ago: in 1975 the weakest herbal cannabis analysed was 0.2%; in 1978 the strongest was 12%. Oh my god: in just three years herbal cannabis has become 60 times stronger."
Butterworth links to some excellent headlines about "killer skunk," too."