The relationship between in-session commitment language and daily self-reported commitment to reduce or abstain from drinking

Background: Motivational interviewing is hypothesized to operate by enhancing a client's internal motivation to change. Past research operationalizes this process by measuring in-session statements for change (i.e., change talk), yet relationships between change talk and other measures of motivation have yet to be substantiated. This study tested whether in-session change talk predicted subsequent reports of commitment to abstain or moderate drinking assessed via ecological momentary assessment (EMA), and explored each of their contributions to drinking outcomes. Method: Secondary data analysis was performed on data from 48 study participants who received therapy within a randomized controlled trial testing mechanisms of actions of MI. Multilevel models were used to test whether in-session commitment statements (strength, frequency, and slope of strength) made in two therapy sessions predicted subsequent daily reports of commitment to abstain or not drink heavily and drinking (21 days of data) in the weeks following each respective session. Results: A weak, negative relationship between in-session commitment and average daily commitment to abstain emerged. No relationship between in-session statements and average daily commitment to not drink heavily emerged. Only EMA commitment predicted drinking outcome. Post hoc analyses demonstrate a moderating impact of EMA commitment to abstain on in-session commitment strength: low pre-treatment commitment to abstain and increasing commitment strength across a session yielded the greatest drink reduction. Conclusion: In-session change talk and EMA commitment may represent distinct aspects of motivation, yet their interaction appears important to treatment prognoses. Commitment to abstain may be important for treatment selection and successful drink reduction.