A systematic review of patient-therapist synchrony as an indicator of emotion regulation in psychotherapy: an integrated approach.

Interpersonal synchrony is increasingly being studied in the context of psychotherapy. The Interpersonal Synchrony (In-Sync) model proposes that patient-therapist synchrony enhances working alliance by promoting emotion regulation (ER). While the link between synchrony and working alliance has been extensively described, its relation to ER in the clinical setting remains underexplored. The present systematic review, therefore, aimed to address this gap by providing a qualitative synthesis of the methods employed and the results reported by studies investigating the relationship between patient-therapist synchrony and ER. A comprehensive search yielded seven studies (out of an initial 2,094), published between 2007 and 2024, encompassing 828 participants (563 patients and 265 therapists). Despite finding highly heterogeneous conceptual frameworks and methodologies employed to assess both synchrony (e.g., motion energy analysis [MEA], electrocardiogram, skin conductance) and ER (e.g., self-report questionnaires and behavioral coding systems), the studies' results revealed a predominantly positive association between synchrony and ER, with in-phase synchrony linked to improved emotional stability and positive emotional experiences. Nonetheless, two studies presented contrasting results, either suggesting a more complex dynamic of co-regulation or finding no direct relationship between nonverbal synchrony and emotional self-regulation. Additionally, a notable research gap was revealed regarding older adults, as no studies included participants over 61 years. Overall, this systematic review highlights the lack of standardized methods and conceptual ambiguity surrounding ER, ultimately limiting cross-study comparability, as well as emphasizing the multiple roles of synchrony in psychotherapy and the need for further research to establish methodological coherence and theoretical consensus in this field.