Copeland 2001.

Methods	Randomised controlled trial Treatment delivered in a university research unit
Participants	229 responders to an advertisement for cannabis treatment were randomised Most members of the sample were male (69.4% of total sample) and were in their early thirties (average 32.3 years) Most members of the total sample were daily cannabis users who used 2 joints per day on average (2.1, 2.0 and 2.2 in Groups 1, 2 and 3, respectively) Cannabis‐related problems were high (scores of 42.4, 42.2 and 45.4 on the CPQ), and participants reported an average score ≥ 9 on the SDS (9.2, 9.8, 9.3). A minority of the total sample had experienced previous cannabis treatment (28.8%) Other substance use was not reported, although participants were excluded if they reported more than weekly use of any drug other than nicotine and alcohol, a score > 14 on the AUDIT or any previous alcohol‐related social problems
Interventions	Group 1: 6‐session CBT over 6 weeks (50% of participants completed treatment as intended, 4.2 sessions were completed on average; n = 78). Sessions lasted 60 minutes. Group 2: single‐session CBT (87.8% of participants received the session; n = 82). This session lasted 90 minutes Group 3: DTC (n = 69) Interventions shared a cannabis‐abstinence goal. Participants were reimbursed with lottery entry to win a $1000 voucher for participation. Therapist training was not well described, but therapists did receive "regular clinical supervision". Treatment fidelity was ensured by audiotaping all sessions and assigning an independent rating of a random schedule of 1 in 10 sessions
Outcomes	Proportion of smoking days; proportion abstinent in the past month; proportion reporting continuous abstinence; number of joints used per day; score on SDS, score on CPQ; mental health on Global Severity Index from SCL‐90‐R
Notes	Follow‐up was provided at an average of 242 days for Group 1, 223 days for Group 2 and 242 days for Group 3. Follow‐up rates at final assessment were not reported by group, but 74.2% of the total sample was assessed Analysis tested for differences by therapist and found no significant effect. An ITT analysis approach was used Study was funded by the Australian Commonwealth Department of Health and Family Services Research into Drug Abuse Grants Program. Study authors reported no declarations of interest
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomisation process not explained
Allocation concealment (selection bias)	Low risk	Participants were centrally allocated; otherwise, concealment procedures were not reported
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participant and personnel blinding was not possible because of the type of intervention provided
Blinding of outcome assessment (detection bias) Subjective outcomes	Low risk	An "independent researcher 'blind' to the subject’s treatment" completed assessments
Blinding of outcome assessment (detection bias) Objective outcomes	Low risk	Urine collected to establish the validity of self report
Incomplete outcome data (attrition bias) All outcomes	Low risk	"For each outcome, additional analyses controlling for the effect of potential confounders on the relationship between treatment condition and outcome were conducted where appropriate." ITT was used
Selective reporting (reporting bias)	Low risk	Pre‐specified outcomes were reported and protocol is shown
Other bias	Low risk	Although participants were excluded if they reported more than weekly drug use, substance use otherwise was not assessed during the trial. No recent treatment or additional treatment was permitted during the trial period; otherwise, it was not assessed. Very few demographics were collected at baseline, although they were reported in a secondary analysis (Copeland 2001b). No other bias was found