Objective Little is known about what may distinguish effective and ineffective group interventions. switch and positive expectancies. Results Sequential analysis indicated that facilitator open-ended questions and reflections of switch talk (CT) improved group CT. Group CT was then followed by more CT. Multilevel models accounting for rolling group enrollment exposed group CT was associated with decreased alcohol intentions alcohol use and heavy drinking three months later on; group sustain talk was associated with decreased motivation to change increased intentions to utilize marijuana and improved positive alcohol and cannabis expectancies. Conclusions Facilitator conversation and peer reactions each had effects on switch and sustain talk in the group establishing which was then associated with individual changes. Selective reflection of CT in adolescent group MI is definitely suggested as a strategy to manage group dynamics and increase behavioral switch. HA14-1 MI with at-risk youth has been recorded in many studies (e.g. Baer Garrett Beadnell Wells & Peterson 2007 D’Amico Kilometers Stern & Meredith 2008 Feldstein & Ginsburg 2006 Spirito et al. 2011 Walker Roffman Stephens Wakana & Berghuis 2006 and recent studies have shown that MI is also a promising treatment for at-risk youth (D’Amico Hunter Kilometers Ewing & Osilla 2013 Engle Macgowan Wagner & Amrhein 2010 Feldstein Ewing Walters & Baer 2012 However many questions remain such HA14-1 as what makes MI ��work��; that is what are the potential mechanisms of action? A central aspect of MI is to help clients who are ambivalent about a problematic behavior deal with their ambivalence preferably in the direction of positive changes in their behavior (Miller & Rollnick 2012 In the last several years experts have begun to examine client conversation during the MI therapy session as one potential explanation for why behavior may switch. Specifically this work offers focused on the quantity or strength of client switch talk; switch talk is defined as any self-expressed conversation that is an argument for switch (Miller & Rollnick 2012 Studies have Il6 examined the switch talk that occurs during a session and how a therapist��s use of MI may impact switch talk and subsequent AOD use (Apodaca & Longabaugh 2009 Briefly findings possess typically demonstrated that client switch talk during a session is associated with reductions in AOD use (Aharonovich Amrhein Bisaga Nunes & Hasin 2008 Bertholet Faouzi Gmel Gaume & Daeppen 2010 Magill Apodaca Barnett & Monti 2010 Martin Christopher Houck & Moyers 2011 Moyers Martin Houck Christopher & Tonigan 2009 Vader Walters Prabhu Houck & Field 2010 Walker Stephens Rowland & Roffman 2011 although a few studies have not found this association (e.g. Gaume Bertholet Faouzi Gmel & Daeppen 2013 Morgenstern et al. 2013 In addition when clients voice sustain talk or arguments against switch this is associated with higher AOD use (Baer et al. 2008 Miller Benefield & Tonigan 1993 Moyers et al. 2007 Vader et al. 2010 and a lower likelihood of methods toward reducing AOD use such as switch plan completion (Magill et al. 2010 Most studies in this area have also demonstrated that more MI-consistent behaviors from your therapist/interventionist such as open questions and reflective listening increase switch talk from the client (Apodaca Magill Longabaugh Jackson & Monti 2012 Daeppen Bertholet & Gaume 2010 Gaume Bertholet Faouzi Gmel & Daeppen 2010 Glynn & Moyers 2010 Morgenstern et al. 2013 Moyers & Martin 2006 In contrast MI-inconsistent behaviors such as confrontation or providing HA14-1 unsolicited advice increase sustain talk (Gaume et al. 2010 Moyers & Martin 2006 Preliminary research in interventions that included clients with problem drinking and their significant others suggests that these effects are not limited to clinician behavior. Specifically significant others�� expressions of support for behavior switch were positively correlated with client switch talk and negatively correlated with sustain talk (Apodaca et al. 2012 Manuel Houck & Moyers 2012 Therefore MI appears to ��work�� by increasing client switch talk during a session which is then associated with positive changes in behavior. Although an understanding of what happens in individual therapy is important in most adolescent AOD treatment settings the group file format is used to help teens.