Single subject repeated measures design of an open label administration of Cannabidiol (CBD) to 5 participants withdrawing from cannabis use in an inpatient setting. 300mg of CBD will be administered once on day 1, twice on days 2-5 and once on day 6. Participants will be discharged on day 7. CBD will be administered orally in capsules.

Inclusion Criteria: Participants must be seeking treatment for cannabis use disorder and report having experienced cannabis withdrawal symptoms in past quit attempts (as defined by participants' experiencing 3 or more symptoms after cessation of prolonged cannabis use or continuing use to avoid withdrawal symptoms). They must meet the criteria for a DSMV current cannabis use disorder and test positive to THC on urinary dip stick test on admission. They must be aged 18-65 and speak English.

Exclusion Criteria: The aim is to exclude individuals with concurrent conditions that jeopardise patient safety or confound study data interpretation. These include (a) presence of another substance use disorder, operationalized as (i) more than twice weekly use of an illicit drug in the last 90 days (other than cannabis), (ii) alcohol AUDIT scores of greater than 15, or a current history of alcohol dependence, (iii) substance use treatment in the last 30 days, or (iv) current prescription drug abuse or dependence (benzodiazepines, opioids or psychostimulants); (b) evidence of unstable or severe medical conditions or cognitive or psychiatric impairment (including developmental disorder, schizophrenia or other psychotic disorders) that may prevent participation; (f) known or suspected allergy to propylene glycol, corn oil; (h) women of child bearing age not on a reliable contraceptive or men intending to start a family with one month of trial participation; (i) pregnant or lactating women; (j) not available for follow-up; (k) no access to telephone; or (l) unwillingness to provide written confirmation that they have been informed about, and will comply with, exclusion from driving when receiving medication. Only persons meeting all criteria will be assessed by trial medical officers and research staff as appropriate.