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 |
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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 |
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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 |
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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 |