Effectiveness of motivational interviewing interventions for adolescent substance use behavior change: a meta-analytic review
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This entry is our analysis of a review or synthesis of research findings considered particularly relevant to improving outcomes from drug or alcohol interventions in the UK. The original review was not published by Findings; click Title to order a copy. Free reprints may be available from the authors – click prepared e-mail. The summary conveys the findings and views expressed in the review. Below is a commentary from Drug and Alcohol Findings.

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Effectiveness of motivational interviewing interventions for adolescent substance use behavior change: a meta-analytic review.

Jensen C.D., Cushing C.C., Aylward B.S. et al.
Journal of Consulting and Clinical Psychology: 2011, 79(4), p. 433–440.
Unable to obtain a copy by clicking title? Try asking the author for a reprint by adapting this prepared e-mail or by writing to Dr Steele at rsteele@ku.edu. You could also try this alternative source.

Not just for adults, but teenagers and young adults too, with this analysis motivational interviewing seems confirmed as the leading evidence-based approach to reducing possibly or actually risky substance use among non-clinical populations not seeking treatment.

Summary Evidence for the effectiveness of motivational interviewing to modify health-related behaviour in adults is strong, but evidence in respect of adolescents is just emerging. For the first time, this meta-analysis A study which uses recognised procedures to combine quantitative results from several studies of the same or similar interventions to arrive at composite outcome scores. Usually undertaken to allow the intervention's effectiveness to be assessed with greater confidence than on the basis of the studies taken individually. aimed to summarise information and synthesise data from studies of motivational interviewing interventions intended to promote changes in the substance use of teenagers and young adults.

The analysts searched for peer-reviewed, English language articles from studies which compared post-treatment outcomes from interventions described as motivational interviewing against those from control A group of people, households, organisations, communities or other units who do not participate in the intervention(s) being evaluated. Instead, they receive no intervention or none relevant to the outcomes being assessed, carry on as usual, or receive an alternative intervention (for the latter the term comparison group may be preferable). Outcome measures taken from the controls form the benchmark against which changes in the intervention group(s) are compared to determine whether the intervention had an impact and whether this is statistically significant. Comparability between control and intervention groups is essential. Normally this is best achieved by randomly allocating research participants to the different groups. Alternatives include sequentially selecting participants for one then the other group(s), or deliberately selecting similar set of participants for each group. conditions such as assessment only or an intervention not intended or expected to affect substance use. The people involved had to be (with minor exceptions) aged 21 or less, though their parents might also be involved in the intervention. With relatively few studies, the analytic method did not assume that the impact of these motivational interventions varied only by chance around one 'true' underlying figure, but that differences between the studies might have led to real differences in the impacts of the interventions.

In all 21 studies were discovered. Most documented changes in cannabis and alcohol use, a third smoking, while lesser proportions reported on other drugs. All but four studies recruited samples who were not attending treatment centres but might for example have been identified as substance users in emergency departments or doctors' surgeries, or responded to requests for substance users to join a study. In line with this sampling, 13 of the 21 studies tested brief interventions consisting of just one session of motivational interviewing, and in 17 the motivational intervention was the sole 'treatment'. Additional to or instead of measuring change shortly after the interventions ended, seven studies conducted follow-up assessments over six months later and another four within the next six months.

Main findings

Measured as effect sizes, A standard way of expressing the magnitude of a difference (eg, between outcomes in control and intervention groups) applicable to most quantitative data. Enables different measures taken in different studies to be compared or (in meta-analyses) combined. Based on expressing the difference in the average outcomes between control and experimental groups as a proportion of how much the outcome varies across both groups. The most common statistic used to quantify this difference is called Cohen's d. Conventionally this is considered to indicate a small effect when no greater than 0.2, a medium effect when around 0.5, and a large effect when at least 0.8. the degree to which the interventions affected substance use varied, but not so much that the studies had to be treated as so different that their results could not be pooled. Though in their own rights only three studies contributed statistically significant results, pooled across all 21, motivational interventions led to a small but statistically significant reduction in substance use amounting to an effect size of about 0.17.

Though still statistically significant, the impact waned when assessed over six months later (effect size of 0.13) compared to assessments less than six months later (effect size of 0.32). When (as it was in five studies) smoking was the sole target, at an effect size of 0.31 the impact was twice as large as the impact on other forms of substance use.

The authors' conclusions

The results of this synthesis of data from studies of young people are consistent with those found among adults. Pooled across all relevant studies, interventions for youth substance use based on motivational interviewing have resulted in small but statistically significant reductions in the use of substances including tobacco, alcohol, cannabis and other illicit drugs, though to a slightly lesser degree when tobacco-only studies were excluded. These results were recorded despite most interventions consisting of just a single session, and most interventionists not having received graduate-level training – features which suggest that motivational interviewing may be a particularly cost-effective approach for non-treatment samples of young substance users. Though impacts waned, they remained statistically significant over six months later, showing that just one or a few sessions can produce sustained substance use reductions.

It should be stressed that these results derived mainly from non-treatment populations and cannot be assumed to apply to young people diagnosed with substance use disorders, who might need more extended and possibly more robust interventions. Moreover, only five of the 21 studies systematically assessed whether the interventions really conformed to the principles of motivational interviewing, and no attempt was made to judge whether any of the studies might have produced biased results. This corpus of studies also offers no clear indication of the degree to which parents should be involved in such interventions.

Nevertheless, the results suggest that motivational interviewing does promote positive change in youth substance use, and that clinicians should consider using this approach as at least as one component of their interventions.

Findings logo commentary With this analysis motivational interviewing seems confirmed as the leading evidence-based approach to reducing possibly or actually risky substance use among non-clinical populations not seeking treatment not just among adults, but teenagers and young adults too. This status partly reflects the relatively intense research effort devoted to the approach, which in turn is a testament to its widespread applicability from possibly risky substance users not seeking help to dependent users attending treatment, and as a standalone treatment, an adjunct to the main treatment, or as a style pervading all client-clinician encounters.

Broadly speaking, what the featured synthesis showed is that (compared to doing nothing or nothing meant to be effective) one or just a few face-to-face counselling sessions intended to be based on motivational interviewing are followed by reductions in substance use among young people who may have been using these substances inadvisably or excessively, but have not been diagnosed as clinical cases, and whose related problems have not been so troubling or noticeable that they have attracted treatment. As the authors comment, this finding accords with that from a synthesis of studies mainly of adults.

But within each study, the impacts were rarely statistically significant and, particularly when tobacco was not the focus, in aggregate very small. With the fact that the comparators were not intended to be active interventions, this raises doubts over whether the motivational nature of the interventions was the active ingredient or whether any acceptable and feasible intervention would have been as effective – or indeed, whether what we are seeing is the pooling of subtle biases in the studies which tipped findings slightly in favour of motivational interviewing.

One riposte to such doubts is that among people not seeking help, motivational interventions (which do not confront or insist that participants accept a clinical label or a pre-determined outcome) are among the few which are acceptable to the participants and feasible – feasible partly because they are acceptable, and partly because they can be quite brief. Another is that we have evidence – from studies of young people among others – that what happens during motivational sessions does matter. In particular, from a British study of further education students and others from Switzerland, it seems that it is important to embody the overall spirit of the approach and, in finer detail, to use the skill of reflective listening to 'play back' to the client an elaborated version of their own comments.

The authors' caution that a brief motivational intervention may be inappropriate and/or insufficient as a formal treatment for young people with a diagnosed problem is supported by a review of such studies of young problem drinkers. It tentatively concluded that the most promising approaches were cognitive-behavioural therapy, family therapy and community reinforcement – the latter two engaging the young person's parents and 'significant others' in the process. These suggestions accord with those made by a review conducted for Britain's National Institute for Health and Clinical Excellence (NICE). In respect of interventions for children and young people who misuse alcohol, it recommended offering individual cognitive-behavioural therapy for those with limited comorbidities and good social support, and multi-component programmes engaging families and the wider social circle for those with significant multiple problems and/or limited social support. Multidimensional Family Therapy in particular has a good research record, but one mainly due to studies conducted by its developers.

Thanks for their comments on this entry in draft to Ric Steele of the University of Kansas in the USA. Commentators bear no responsibility for the text including the interpretations and any remaining errors.

Last revised 06 February 2012

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