Fidelity to Motivational Interviewing and subsequent cannabis cessation among adolescents.

This study tested whether differences in cannabis cessation 3 months after a single session of Motivational Interviewing (MI) may be attributable to fidelity to MI. All audio-recordings with necessary 3-month follow-up data (n=75) delivered by four individual practitioners within a randomised controlled trial (RCT) were used. Participants were weekly or more frequent cannabis users aged 16-19 years old in Further Education colleges. All tapes were coded with the Motivational Interviewing Treatment Integrity (MITI) scale Version 2 by 2 coders. Satisfactory inter-rater reliability was achieved. Differences between and within practitioners in fidelity to MI were consistently detected. After controlling for practitioner effects, Motivational Interviewing spirit and the proportion of complex reflections, were independently predictive of cessation outcome. No other aspects of fidelity were associated with outcome. Two particular aspects of enhanced fidelity to MI are predictive of subsequent cannabis cessation 3 months after a brief intervention among young cannabis users.