The "dyadic dance": Exploring therapist-client dynamics and client symptom change using actor-partner interdependence modeling and multilevel mixture modeling.

Using longitudinal actor-partner interdependence modeling and multilevel mixture modeling, the aims of this study were to investigate the therapist-client dyadic dynamic patterns (i.e., therapist and client consistency and their mutual influences in perceptions of working alliance) and how these dynamic patterns related to client symptom change with varied treatment lengths. Data set included 1,520 sessions conducted by 85 master's level therapist trainees with their 283 clients in China. Before every session, clients reported their symptom; after every session, both therapists and clients rated their working alliance. (a) Therapist consistency was positively associated with greater client symptom improvement, especially in relatively longer therapy course. (b) Client consistency and therapist-client mutual influence dynamics did not individually relate to client symptom improvement. (c) Two subgroups of therapist-client dyads with distinct dyadic dynamic patterns were identified: one subgroup (Dyadic Independence) showing significant self-consistency and nonsignificant mutual influence and the other subgroup (Mutual Influence) showing significant self-consistency as well as mutual influence. (d) The mutual influence subgroup was associated with greater client improvement than the dyadic independence subgroup, especially in shorter therapy. A dyadic dynamic pattern characterized by the presence of therapist and client self-consistency as well as mutual influence may be conducive to positive therapeutic outcome in terms of client symptom improvement. (PsycInfo Database Record (c) 2021 APA, all rights reserved).