DISCUSSION
paranoid’, ’
SECONDARY, DRUG INTERACTION, DRUG EFFECT
We carried out the first controlled experiment testing the acute effects of vaporised cannabis with and without cannabidiol in both adolescents and adults. On our three primary outcomes, subjective ‘feel drug effect’, verbal episodic memory and psychotomimetic effect, we found no evidence that age group moderated the impact of cannabis. Furthermore, Bayesian analyses supported these null results. Additionally, we found no evidence that vaporised CBD (24 mg for a 75 kg person) modulated the acute impact of vaporised THC (8 mg for a 75 kg person) on our primary outcome variables. Our results were supported by analysis of our secondary outcome variables, which showed, almost unanimously, that there were null moderating effects of age group and CBD. The mostly consistent pattern of results was (i) ‘THC’ and ‘THC + CBD’ produced expected changes from ‘PLA’; (ii) ‘THC’ and ‘THC + CBD’ did not differ from one another; and (iii) the impact of cannabis did not differ in adolescents and adults.Based on Mokrysz On our primary outcome variables, CBD did not significantly moderate the acute effects of THC. This is in line with previous controlled cannabis vaporisation experiments [However, there were some notable exceptions to the primarily null findings. First, there was some limited evidence that ‘THC + CBD’ produced stronger effects than ‘THC’: ‘feel drug effect’ was half a point greater on ‘THC + CBD’ compared to ‘THC’, when collapsing across all timepoints, and this was supported by an area‐under‐the‐curve difference too; the PSI cognitive disorganisation subscale was greater by ~2 points on ‘THC + CBD’ compared to ‘THC’; and heart rate was greater on ‘THC + CBD’ than ‘THC’ by 8 beats/min. To contextualise these differences, the ‘THC’ versus ‘PLA’ conditions gave differences of 4.5 points, 4 points and 18 beats/min, respectively. Notably, these were secondary outcome variables. They should also be considered against a backdrop of null CBD moderation effects on ‘like drug’, ‘dislike drug’, ‘paranoid’, ‘want cannabis’, all other PSI subscales, prose recall performance and both positive and negative PANSS scores. The supplementary analyses of area‐under‐the‐curve and peak subjective effects (Mean THC plasma concentrations at T2 for ‘THC’ (15 ng/mL) and ‘THC + CBD’ (28 ng/mL) conditions (Table We also detected an age‐group by drug interaction for CBD plasma level, in which adults had greater CBD levels than adolescents (Our study has numerous strengths. In addition to its novelty, we biochemically verified drug abstinence; we improved on previous work by matching adolescent and adult users on cannabis use; including equal numbers of men and women; and we powered our study to detect an age‐group by drug interaction and took account of winner's curse [Our findings have important scientific, policy and educational implications. First, they cast doubt on the claim that adolescent cannabis users are more vulnerable to some short‐term effects of cannabis than adult cannabis users. Second, our results add further weight to the claim that doses of vaporised CBD, which are near to naturally occurring levels, do not mitigate the acute harms of THC [