PREFERENCE FOR HIGH-POTENCY VERSUS LOW-POTENCY MARIJUANA

With many drugs of abuse, humans and other species display a preferenc e for higher doses (or more potent dosage forms) over lower doses (or less potent dosage forms). The present study was designed to determine whether this generalization would hold for marijuana smoking by human s. Twelve regular marijuana smokers participated in two independent an d identical choice trials in which, on separate sessions, they first s ampled marijuana of two different potencies (0.63% and 1.95% delta-9-t etrahydrocannabinol; THC) and then, on the next session, chose which o f the two, as well as how much, to smoke. During sampling sessions, th e high-potency marijuana produced a greater heart rate increase and gr eater subjective effects than the low-potency marijuana. Subjects chos e the high-potency marijuana significantly more often than the low-pot ency marijuana (21 out of 24 choice occasions). These results support the hypothesis that the reinforcing effects of marijuana, and possibly its abuse liability, are positively related to THC content.