Reducing the Harmful Effects of Cannabis Use: Finding the Optimal CBD:THC Ratio

This study will recruit healthy volunteers who use cannabis infrequently. Each participant will attend the laboratory on five occasions: an initial visit to check that they are safe to join the study and four days of testing. Participants will be administered, in a randomized order, vaporized cannabis containing one of four different ratios of CBD:THC (0:1, 1:1, 2:1, 3:1). The cannabis administration will follow a standardised inhalation procedure using a medical-grade vaporizer device. Participants will complete a series of tasks measuring cognition, psychosis, anxiety and other subjective experiences. The study will be carried out at the NIHR-Wellcome Trust Clinical Research Facility at King's College Hospital.