Flexible and multimodal synchrony during psychotherapy for depression: Addressing the mixed synchrony–outcome findings.

Dyadic synchrony, the alignment in time of partners' behavioral, physiological, and emotional processes, has often been related to better psychotherapy outcome. However, conflicting findings on this association have recently emerged. Drawing on the theory of flexible multimodal synchrony, we examined five different synchrony modalities to explore the role of flexibility in synchrony (FS), the fluctuations in synchrony over time, in the synchrony-outcome association. We computed synchrony and FS in body movement, facial expression, heart rate, respiratory sinus arrhythmia, and electrodermal activity in 58 patients and their therapists during five preselected sessions during psychodynamic psychotherapy for depression. Patients reported their well-being before and after each session. The findings suggested that greater body movement FS predicted better session outcomes. Facial expression FS moderated the synchrony-outcome association, in that higher synchrony predicted better outcomes when FS was high and poorer outcome when FS was low. No effects were found for the physiological modalities. Group iterative multiple model estimation showed no significant associations between synchrony modalities at the sample level. These results appear to point to the independence of synchrony in different modalities and highlight the potential of behavioral FS in clarifying the synchrony-outcome association. (PsycInfo Database Record (c) 2026 APA, all rights reserved).