The seed and the soil: effect of dosage, personality and starting state on the response to delta 9 tetrahydrocannabinol in man.

1 The effects of two doses of delta 9THC (2.5 and 10 mg), delivered by paced smoking of herbal cigarettes, on CNV magnitude, subjective mood ratings and heart rate were studied in 20 subjects. 2 There were highly significant interactions between drug dosage and Extraversion and Neuroticism scores, so that the direction and degree of response to the different doses of delta 9THC depended on the personality characteristics of the subjects. 3 The effects of 9 mg delta 9THC and placebo, delivered in herbal cigarettes smoked naturally, on smoking behaviour, subjective mood ratings, measures of autonomic activity and auditory and visual cortical evoked responses were compared in 12 subjects. 4 Smoking behaviour, subjective 'high' rating and elevation of heart rates were the most significant discriminators between drug and placebo. The latency of some of the components of the visual evoked responses was also increased by delta 9THC. 5 There was a significant correlation between the effects of delta 9THC on skin conductance reactivity and the basal (pre-drug) level, reactivity increasing after drug in subjects with low basal reactivity and decreasing in those with high basal levels. 6 Both experiments provided clear evidence of dose-dependent biphasic stimulant and depressant actions of delta 9THC on both subjective and objective measures, and these effects were influenced by the personality and the starting state of the subjects.