Solowij, N.Broyd, S.Greenwood, L.M.van Hell, H.Martelozzo, D.Rueb, K.Todd, J.Liu, Z.Galettis, P.Martin, J.Murray, R.Jones, A.Michie, P.T.Croft, R.2023-08-182023-08-182019European Archives of Psychiatry and Clinical Neuroscience: official organ of the German society for biological psychiatry, 2019; 269(1):17-350940-13341433-8491https://hdl.handle.net/2440/139172Access to cannabis and cannabinoid products is increasing worldwide for recreational and medicinal use. Two primary compounds within cannabis plant matter, Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD), are both psychoactive, but only THC is considered intoxicating. There is significant interest in potential therapeutic properties of these cannabinoids and of CBD in particular. Some research has suggested that CBD may ameliorate adverse effects of THC, but this may be dose dependent as other evidence suggests possible potentiating effects of THC by low doses of CBD. We conducted a randomised placebo controlled trial to examine the acute effects of these compounds alone and in combination when administered by vaporisation to frequent and infrequent cannabis users. Participants (n = 36; 31 male) completed 5 drug conditions spaced one week apart, with the following planned contrasts: placebo vs CBD alone (400 mg); THC alone (8 mg) vs THC combined with low (4 mg) or high (400 mg) doses of CBD. Objective (blind observer ratings) and subjective (self-rated) measures of intoxication were the primary outcomes, with additional indices of intoxication examined. CBD showed some intoxicating properties relative to placebo. Low doses of CBD when combined with THC enhanced, while high doses of CBD reduced the intoxicating effects of THC. The enhancement of intoxication by low-dose CBD was particularly prominent in infrequent cannabis users and was consistent across objective and subjective measures. Most effects were significant at p < .0001. These findings are important to consider in terms of recommended proportions of THC and CBD in cannabis plant matter whether used medicinally or recreationally and have implications for novice or less experienced cannabis users.en© Springer-Verlag GmbH Germany, part of Springer Nature 2019.Δ9 -Tetrahydrocannabinol (THC); Cannabidiol (CBD); Cannabis; Cannabinoids; Intoxication; Synergistic effectsHumansCannabisPerceptual DisordersCannabidiolDissociative DisordersBlood PressureHeart RateDrug InteractionsAdolescentAdultMiddle AgedFemaleMaleYoung AdultSelf ReportCannabinoid Receptor ModulatorsDronabinolDrug-Related Side Effects and Adverse ReactionsJournal article10.1007/s00406-019-00978-22023-08-18652180Jones, A. [0000-0002-1105-6195]