Some versions of this legend claim the potency change is due to "genetic modification," a term which often evokes fear in the popular consciousness, but there is no hard evidence that anything other than selective breeding and enhanced growing techniques are behind the change.
Another claim about cannabis is that impairment due to smoking it lasts many days after using it, since THC is stored in the fat cells, leading to a low-grade haze long after the primary high is gone [REF].