A randomized controlled trial to influence client language in substance use disorder treatment.

Background: Client language is hypothesized to be a mechanism of action in motivational interviewing (MI). Despite the association of change and sustain talk with substance treatment outcomes, it not known whether providers can intentionally influence this language as hypothesized.

Objective: This is a randomized controlled trial to investigate whether substance use providers can be trained to influence client language.

Methods: Treatment providers specializing in substance use disorders (n=190) were randomly assigned to standard training in MI (MI-AU) or training emphasizing an influence of client language (MI-LEAF). Treatment sessions with actual clients were evaluated 3, 6 and 12 months after training by masked raters. Frequencies of client change and sustain talk were the outcome variables.

Results: Sustain talk, but not change talk, was significantly lower in clients whose providers had received the specialized training (b=-0.175, SE=0.087, p=0.046, CI[-0.348 to 0.002], d=-0.325). Mediation analyses supported a causal chain between a) training, b) providers' attempts to minimize sustain talk in treatment sessions via directive reflective listening and c) client sustain talk in the treatment session (κ=0.0833, bootstrap SE=0.0394, 95% CI [0.0148, 0.1691]).

Conclusions: With specialized training, providers can reduce the amount of opposition language their clients offer when considering a change in their substance use. Demonstrating that client language is under partial control of the provider supports the feasibility of clinical trials to investigate the impact of shaping client language on treatment outcomes.