Group Dynamics: Theory, Research, and Practice, Vol 30(1), Mar 2026, 16-29; doi:10.1037/gdn0000243
Objective: The therapeutic alliance is considered to be one of the most salient common factors in group psychotherapy, including within interpersonal psychotherapy groups (IPT-G). More recently, scholars are emphasizing the distinction between state- (within-person) and trait-like (between-person) alliance in both individual and group psychotherapies (Kivlighan et al., 2022; Zilcha-Mano & Fisher, 2022). Despite the abundant literature supporting the efficacy of IPT-G, there is limited understanding of the mechanisms of change that facilitate these outcomes, including alliance to the group. The purpose of this study was to investigate the relationship between state- and trait-like alliance and therapeutic outcomes in IPT-G. Method: Data for this study were provided by 56 patients receiving care within a community mental health facility in Canada. Patients participated in weekly sessions of IPT-G for 10 weeks and completed the Outcome Rating Scale (Miller et al., 2003) and the Group Session Rating Scale (Quirk et al., 2013) after each session for routine outcome monitoring. Results: Results indicated significant and positive state- and trait-like alliance effects, indicating the importance of both session-to-session fluctuations in alliance, as well as patients’ interpersonal skills and capacities before they begin IPT-G. The exploratory two-way interaction between within-person alliance and between-person alliance on outcome was also positive and significant, indicating that an increase in state-like alliance was related to better outcomes for that member if they also reported high levels trait-like alliance. Conclusions: Findings from this study demonstrate the importance of both state- and trait-like alliance in IPT-G and position the alliance as a treatment specific factor of change in IPT-G. Clinical implications will be discussed. (PsycInfo Database Record (c) 2026 APA, all rights reserved)