CONSORT diagram.
MAY
Diagram showing enrolment, allocation, and the groups at each stage of analysis.All data was collected at the Clinical Psychopharmacology Unit (University College London, London, UK). The first stage of the trial occurred from May 28, 2014, to August 12, 2015, and the second stage occurred from May 24, 2016, to January 12, 2017. The final follow-up assessment was completed on June 5, 2017, and the trial ended on May 30, 2018, due to a lack of funding for a subsequent phase 2b stage. The trial was preregistered prior to data collection with the EU Clinical Trials Register (2013-000361-36) and with clinicaltrials.gov (NCT02044809). The trial was approved by the UK Health Research Authority (13/EE/0303) and the UK Medicines and Healthcare Regulatory Agency (20363/0325/001-0001). For the protocol see Sample sizes for this trial were informed by a pilot study testing the effects of a 1-week course of CBD on cigarette consumption in tobacco smokers who intended to quit. The effect of CBD on cigarette cessation and cannabis cessation may be comparable as some of CBD’s potential effects are non-drug specific. For example, CBD is thought to produce anxiolytic effects [