Bidirectional affective influences in psychotherapy: A linguistic case analysis of therapist-client moment-to-moment emotional tones and session outcome.

Focusing on emotion is a defining feature of psychodynamic theory; however, few studies have examined emotional synchrony at a fine-grained temporal level and linked these processes with session outcomes. This single-case study investigated turn-by-turn emotional tone synchrony between client and therapist across 38 sessions of open-ended psychodynamic psychotherapy conducted in a community clinic. Emotional tone was operationalized as the ratio of positive to negative emotion words, derived from 2,929 therapist and client speaking turns using the Linguistic Inquiry and Word Count system. Dynamic structural equation modeling was used to estimate within-session autoregressive effects and cross-lagged parameters indexing therapist-to-client and client-to-therapist emotional influence. Results indicated significant bidirectional emotional synchrony, with therapist emotional tone predicting subsequent client emotional tone and client emotional tone predicting subsequent therapist emotional tone, controlling for autoregressive effects. At the between-session level, stronger therapist-led synchrony was associated with higher client-rated session outcomes, whereas client-led synchrony was not. In addition, greater therapist emotional granularity, operationalized as variability in therapist emotional tone across speaking turns, was associated with higher client-rated session outcomes. These findings provide idiographic support for dynamic emotional synchrony in a manner consistent with psychodynamic models of affective attunement. Moreover, the use of a language-based index of emotional synchrony highlights clinically observable and potentially modifiable emotional processes because therapists can intentionally shape their emotional language while directly observing the emotion words used by clients. Implications for psychotherapy process research, training, and clinical practice are discussed. (PsycInfo Database Record (c) 2026 APA, all rights reserved).