Interpersonal Change as a Mediator of the Within- and Between-Patient Alliance-Outcome Association in Two Treatments for Generalized Anxiety Disorder

Objective: Although a better therapeutic alliance associates with treatment outcome, it may do so in different ways. For example. alliance quality may promote improvement as it shifts over time (within-patient changes); alternatively, alliance quality may also, or instead, influence outcome when generally higher or lower for some patients relative to others (between-patient differences). Although both components have been linked to patient improvement, the distinct mechanisms of these associations have been rarely examined. Conceptually, it follows that within-patient alliance fluctuations (representing the changing nature of a current relationship intended to be ameliorative) may facilitate other interpersonal improvements that could, in turn, translate into symptom reduction. This path squares with the corrective relational experience notion. In contrast, whereas as patients' average alliances across therapy may generally facilitate or hinder improvement, the mechanism may not be other relationship functioning. This squares with the notion that when people generally experience good alliances with their therapist, it may reflect an existing relational ability that catalyzes the effectiveness of other nonrelational therapeutic means. This study tested these distinct hypotheses. Method: Patients (N = 85) with generalized anxiety disorder were randomly assigned to cognitive-behavioral therapy, either alone or integrated with motivational interviewing. They rated alliance quality, interpersonal problems, and outcome repeatedly. Results: Using multilevel structural equation modeling, both within- and between-patient alliances related to subsequent worry reduction. As predicted, change in interpersonal problems mediated the association only at the within-patient level. Conclusions: Results contribute to the literature on mechanisms of the within- and between-person alliance-outcome association.