Deterioration over time in effect of Motivational Interviewing in reducing drug consumption and related risk among young people.
OBJECTIVE
To test whether beneficial effects of a single session of Motivational Interviewing (MI) on alcohol, tobacco and illicit drug use apparent after 3 months were maintained until 12 months.


METHODS
Cluster randomized trial, allocating 200 young people in the natural groups in which they were recruited to either MI (n = 105) or to an assessment-only control condition (n = 95).


METHODS
Ten further education colleges across inner London.


METHODS
Two hundred young people who were current users of illegal drugs (age range 16-20 years) with whom contact was established through peers trained for the project.


METHODS
The intervention was adapted from MI in the form of a topic-based 1-hour single-session discussion.


METHODS
Changes in cigarette, alcohol, cannabis and other drug use and perceptions of risk and harm between the time of recruitment and follow-up interviews after 3 and 12 months.


RESULTS
A satisfactory follow-up rate (81%) was achieved. After 12 months, 3-month differences between MI and assessment-only groups have disappeared almost entirely. Unexpected improvements by the assessment-only control group on a number of outcomes suggest the possibility of reactivity to the research assessment at 3-month follow-up.


CONCLUSIONS
In the terms of the original experiment, there is little evidence of enduring intervention effectiveness shown by between-group differences after 12 months. Deterioration of effect is the most probable explanation, although reactivity to 3-month assessment, a late Hawthorne effect, cannot be ruled out.
McCambridge
Jim
J
National Addiction Centre (The Maudsley/Institute of Psychiatry), London, UK. J.McCambridge@iop.kcl.ac.uk
Strang
John
J
D000293:Adolescent; D000328:Adult; D016000:Cluster Analysis; D005108:Extinction, Psychological; D005260:Female; D006801:Humans; D007406:Interview, Psychological / Q000379:methods* / Q000592:standards; D008297:Male; D009042:Motivation; D011614:Psychotherapy, Brief / Q000379:methods* / Q000592:standards; D012306:Risk; D019966:Substance-Related Disorders / Q000517:prevention & control / Q000628:therapy*; D011795:Surveys and Questionnaires