Procedure (Fig. 
At baseline, participants were assessed for study eligibility, and practiced the inhalation procedure. At baseline and all experimental visits, urine drug and pregnancy screen as well as alcohol and carbon monoxide breath tests (<10 ppm CO to verify 12 h tobacco abstinence) were completed. Participants were asked to avoid using cannabis and all other illicit drugs during the entire course of the study, including the periods between sessions.Timeline of baseline and experimental sessions (baseline did not include bloods or return to sobriety).Prior to each experimental visit participants had their usual breakfast and amount of caffeine – caffeine was not allowed again until completion of cognitive tests. An intravenous cannula was inserted before participants were administered vaporised cannabis (detailed below). Fifteen minutes after the completion of cannabis inhalation, participants completed a battery of cognitive tasks (30–35 min). This was followed by assessments of pleasurable responses to cannabis as well as a ‘hospital walk’ (15 min), a task previously been found to increase paranoia following THC [