McCambridge 2008.

Methods	RCT.
Participants	326 young cannabis users aged 16‐19 years not seeking help from eleven London Further Education colleges. UK.
Interventions	Single session intervention of MI (n= 164) vs drug information and advice giving (n= 162).
Outcomes	Physiological primary: None (but bogus pipeline). Non‐physiological primary: 30‐day frequency of cannabis use (joints past week), 30‐day alcohol consumption (units of alcohol past week + AUDIT score). Secondary: None. Follow‐ups were at 3 and 6 months.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Computerised individual randomisation was undertaken by the local clinical trials unit."
Allocation concealment (selection bias)	Low risk	"Decisions were communicated on an individual basis via telephone or e‐mail to researchers after recruitment and baseline data collection to preserve allocation concealment."
Blinding (performance bias and detection bias) Patients and providers	Unclear risk	No blinding but bogus pipeline.
Blinding (performance bias and detection bias) Assessors	Low risk	"Study participants self‐completed questionnaires which were distributed by a researcher who was blind to study allocation."
Incomplete outcome data (attrition bias) All outcomes	Low risk	17% and 19% lost to follow‐up at 3 and 6 months, respectively. Unequal between groups. Reasons for loss‐to‐follow‐up not stated. Intention to treat using last observation carried forward.
Selective reporting (reporting bias)	Low risk	The published report included all expected outcomes based on the stated hypotheses.
Other bias	Low risk	A bogus pipeline approach was used in addition to self‐report. There were no differences between groups at baseline. No additional sources of bias appears to be present.