ENGLISH :
Aims: To investigate whether a stimulant- and alcohol-focused brief motivational intervention induces positive behaviour change among young, regular users of MDMA ('ecstasy'), cocaine powder and crack cocaine. Design and measurements: A randomized trial of the intervention versus a control group who received written health risk information materials only. All participants completed a baseline self-assessment questionnaire before randomization. Outcome measures were self-reported period prevalence abstinence from ecstasy, cocaine powder and crack cocaine and the frequency and amount of stimulant and alcohol use in the previous 90 days, recorded at 6-month follow-up via self-completion questionnaire and personal interview. Participants and setting A total of 342 adolescent and young adult stimulant users (aged 1622 years) were recruited and 87% were followed-up. The intervention was delivered by a team of 12 agency youth drug workers and two researchers at five locations in Greater London and south-east England. Findings: There were no significant differences in abstinence for ecstasy, cocaine powder or crack cocaine use between the experimental and control groups. Contrasting follow-up with baseline self-reports, there were no between-group effects for changes in the frequency or amount of stimulant or alcohol use. Participant follow-up data suggested that the baseline assessment was a contributing factor in within-group behaviour change among experimental and control condition participants. Conclusions: Our brief motivational intervention was no more effective at inducing behaviour change than the provision of information alone. We hypothesize that research recruitment, baseline self-assessment and contact with study personnel are influences that induce positive reactive effects on stimulant use. (Author' s abstract)