Marsden 2006.

Methods	Multisite RCT (5 sites).
Participants	342 UK adolescent and young adult stimulant users.
Interventions	BMI (n= 166) vs written health risk information (n= 176).
Outcomes	Physiological primary: None. Non‐physiological primary: Ecstasy number of days, ecstasy tablets, cocaine powder number of days, cocaine g/day, crack number of days, crack g/day, cannabis number of days, cannabis g/day, alcohol number of days, alcohol g/weekday, alcohol g/weekend. Secondary: None.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"two‐group randomised controlled trial".
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	"To guard against bias, all follow‐up interviews were conducted by a different worker from the one who administered the participant's recruitment protocol."
Incomplete outcome data (attrition bias) All outcomes	Low risk	13% attrition at 6 months follow‐up, balanced across conditions. Reasons not provided. "The analysis of outcome was conducted on an intention‐to‐treat (ITT) basis (involving all participants who were randomly assigned) and baseline scores were substituted for cases lost to follow‐up."
Selective reporting (reporting bias)	Low risk	The published report included all expected outcomes based on the study hypotheses.
Other bias	Low risk	Stimulant toxicology testing on a random 30%. There were no differences between groups at baseline. No additional sources of bias appear to be present.