The predictive capacity of self-reported motivation vs. early observed motivational language in cognitive behavioural therapy for generalized anxiety disorder.

Client motivation to change is often considered a key factor in psychotherapy. To date, research on this client construct has largely relied on self-report, which is prone to response bias and ceiling effects. Moreover, self-reported motivation has been inconsistently related to treatment outcome. Early observed client in-session language may be a more valid measure of initial motivation and thus a promising predictor of outcome. The predictive ability of motivational factors has been examined in addiction treatment but has been limited in other populations. Addressing this lack, the present study investigated 85 clients undergoing cognitive behavioural therapy (CBT) alone and CBT infused with motivational interviewing (MI-CBT) for severe generalized anxiety disorder. There were two aims: (1) to compare the predictive capacity of motivational language vs. two self-report measures of motivation on worry reduction and (2) to examine the influence of treatment condition on motivational language. Findings indicated that motivational language explained up to 35% of outcome variance, event 1-year post-treatment. Self-reported motivation did not predict treatment outcome. Moreover, MI-CBT was associated with a significant decrease in the most detrimental type of motivational language compared to CBT alone. These findings support the importance of attending to in-session motivational language in CBT and learning to respond to these markers using motivational interviewing.