Stephens 2007.

Methods	RCT.
Participants	188 US marijuana users.
Interventions	1. Personalized feedback (utilising MI) (n= 62) 2. educational control (multi‐media feedback) (n= 62) 3. delayed feedback (n= 64).
Outcomes	Physiological primary: None. Non‐physiological primary: Days of marijuana use per week, periods smoked per day, dependence symptoms. Secondary: Motivation (Readiness to Change Questionnaire). Data not reported.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Used an urn randomisation program.
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	Low risk	"...research staff...was not aware of assigned condition".
Incomplete outcome data (attrition bias) All outcomes	Low risk	Attrition was 5% at 7 weeks, 10% at 6 months, and 19% at 12 months follow‐up. Balanced across conditions. No reasons. ITT probably performed (missing data were replaced with baseline values).
Selective reporting (reporting bias)	Low risk	The published report included all expected outcomes based on the study hypotheses.
Other bias	Low risk	Urine specimens were collected at each assessment point and analysed for the presence of drug metabolites via enzyme immunoassay tests. Differences between groups at baseline were not reported. No additional sources of bias appear to be present.