Participants
CUD, DSM-5, psychotic disorder, allergies
ALLERGIES
Participants were recruited through website advertisements, forums and through flyers in the local community. They met the following inclusion criteria: aged 16–60, CUD of at least moderate severity (≥ 4 symptoms, assessed by clinical interview for DSM-5 symptoms, conducted by trained psychologists), capacity to give written informed consent, expressed a desire and intention to stop using cannabis within the upcoming month, had one or more unsuccessful prior attempts to quit their cannabis use, co-administered cannabis with tobacco, provided a positive urine sample for THC-COOH and for women, provided a negative pregnancy test within the 7 days prior to starting treatment. Women of childbearing potential and all men were required to use an effective method of contraception (oral, injected, implemented, barrier or true abstinence), from the time of consent until 6 weeks after the end of treatment. Initial criteria for participants to be aged 16–26, with vital signs within normal limits were removed early in the trial to increase the generalisability of findings. Exclusion criteria included the following: (1) current pregnancy or breastfeeding, (2) allergies to CBD, microcrystalline cellulose or gelatine, (3) prescribed psychotropic drug use, (4) use of illicit drugs (other than cannabis) 2 or more times per month at screening, (5) inaccurate self-reported drug use confirmed by a positive urine test for drugs that were not reported during screening, (6) current or previous self-reported diagnosis of a psychotic disorder, (7) physical health problem deemed clinically significant and (8) not speaking English.