MarijuanaTP 2004.

Methods	Multisite RCT (3 sites).
Participants	450 US cannabis dependent adults.
Interventions	1. 2 session MET (n= 146) 2. 9 session MET (n= 156) 3 4 month delayed treatment (n= 148).
Outcomes	Physiological primary: None. Non‐physiological primary: Percent of days smoking, periods smoked per day, joints per day, dependence symptoms, abuse symptoms, marijuana problems. Secondary: None.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Urn randomisation.
Allocation concealment (selection bias)	Unclear risk	Insufficient information to permit judgment.
Blinding (performance bias and detection bias) Patients and providers	Unclear risk	No blinding but the outcome measurements are not likely to be influenced by lack of blinding due to validation with physiological measurement.
Blinding (performance bias and detection bias) Assessors	Unclear risk	"Research assistants were not blinded to the participants' experimental conditions." But the outcome measurements are not likely to be influenced by lack of blinding due to validation with physiological measurement.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow‐up at 4 months, 9 months and 15 months were 11%, 13% and 17%, respectively. Balanced. No reasons for loss reported. ITT performed (analysis of missing cases using baseline values.)
Selective reporting (reporting bias)	Low risk	The published report included all expected outcomes based on the study hypotheses.
Other bias	Unclear risk	Collateral interviews and urine specimens to check on self‐report. Numbers of sessions were confounded with differential content and process. Different expectancies of success were created by the differences in treatment length. There were no differences between groups at baseline.