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Therapist-Level Moderation of Within- and Between-Therapist Process-Outcome Associations

Objective: Although higher-quality patient-therapist alliance and more positive patient outcome expectation (OE) consistently predict improvement in psychotherapy, most research has failed to capture the inherent nuance in these process-outcome relations by parsing them into within-therapist (i.e., differences between patients treated by the same therapist) and between-therapist (i.e., differences between therapists’ average process/outcome ratings across all patients in their caseloads) components. Moreover, the few studies that have done so have produced mixed results, suggesting the possibility of systematic variability in these associations (i.e., moderators). One potential source of such variability could be providers themselves; that is, different therapists could use these processes to differing therapeutic benefit. In this vein, the present study had three primary aims. First, I tested the alliance- and OE-outcome associations at both the within- and between-therapist levels. Second, I examined whether the within-therapist alliance- and OE-outcome associations varied among therapists. Third, I explored therapist-level moderators (i.e., theoretical orientation, self-perceived alliance- and OE-strategy usage, and self-perceived alliance- and OE-fostering effectiveness) of the within- and between-therapist alliance- and OE-outcome associations. Finally, as an ancillary question, I explored whether the two components of the process-outcomes associations interacted to predict treatment outcomes; namely, does the extent to which patient-level variability in alliance and OE correlates with improvement (within-therapist component) differ as a function of therapists’ general abilities (across all patients) to foster positive alliances and OE (between-therapist component)? Method: Data derived from 212 adult outpatients treated naturalistically by 42 psychotherapists as part of a randomized trial that compared different case assignment methods. Patients completed measures of alliance, OE, and outcome repeatedly throughout treatment, and therapist rated their characteristics at baseline. I used multilevel structural equation models to test the primary and ancillary research questions. Results: Regarding aim 1, higher-quality between-therapist alliance was associated with greater caseload-level improvement (0.62, SD = 0.29; 95% credible interval [CI] = 0.003, 1.10), whereas within-therapist alliance was unrelated to patient-level improvement (0.38, SD = 0.20; 95% CI = -0.07, 0.75). Although between-therapist OE was unrelated to caseload-level improvement (2.64, SD = 1.69; 95% CI = -0.67, 6.20), more optimistic OE was associated with greater patient-level improvement (0.84, SD = 0.35; 95% CI = 0.15, 1.53). Regarding aim 2, both within-therapist process-outcome associations varied significantly among therapists. Regarding aim 3, therapists’ self-perceived alliance-fostering effectiveness moderated the within-therapist alliance-outcome association (-0.76, SD = 0.24; 95% CI = -1.18, -0.28), whereas identification with a cognitive behavioral orientation moderated the between-therapist alliance-outcome association (-0.46, SD = 0.23; 95% CI = -0.96, -0.004). Taken together, the alliance may have stronger within-therapist associations with improvement in the hands of therapists who are humbler in assessing their own alliance-fostering abilities, and stronger between-therapist associations with improvement for therapists who do not identify strongly with a cognitive behavioral orientation. Finally, regarding the ancillary aim, the within- and between-therapist process components did not have a significant interactive effect on treatment outcomes. Conclusions. Results indicate that different therapists use theory-common treatment processes to differing therapeutic benefit, which can inform more personalized clinical practices and trainings.