Outcome expectations and associated treatment outcomes in motivational enhancement therapy delivered in English and Spanish.

Background And Objectives: The relationship between patients' baseline expectations regarding treatment outcome and actual outcomes has not been widely studied within the field of substance use disorders. We hypothesized that outcome expectations would be unrelated to outcomes in a study investigating motivational enhancement therapy delivered in English (MET-E) consistent with our earlier work, and conducted exploratory analyses in a separate study that investigated the same treatment delivered in Spanish (MET-S).

Methods: These secondary analyses compared patient outcome expectations and substance use treatment outcomes in two large, multisite randomized controlled clinical trials that evaluated three sessions of MET-E or MET-S. The MET-E sample included 461 participants and the MET-S sample included 405 participants. Outcome expectations were measured by a single item regarding expectations about abstinence prior to initiating treatment.

Results: Outcome expectations were strongly associated with most substance use outcomes in the MET-S trial (but not in MET-E), even after controlling for severity of substance use at baseline. In MET-S, those who indicated that they were "unsure" that they would achieve abstinence during treatment submitted a greater percentage of drug-positive urine toxicology screens during the treatment period than those who were 'sure' they would achieve abstinence (F = 18.83, p < .001).

Discussion And Conclusions: Patients' outcome expectations regarding the likelihood of abstinence may be an important predictor of drug use treatment outcomes among Spanish-speakers, but not necessarily for English-speakers.

Scientific Significance: Individual differences and cultural factors may play a role in the association between outcome expectations and treatment outcomes.