The playful mediator, moderator, or outcome? An integrative review of the roles of play and playfulness in adult-centered psychological interventions for mental health.

How do play and playfulness contribute to adult mental health? We evaluated empirical evidence from 20 psychological interventions through a lens emphasizing playfulness in participants and playing processes as a putative change agent. We found (1) preliminary evidence supporting play as a causal agent of positive changes in adult mental health, likely via two mechanisms—as a mediator and as a medium, and (2) limited, unclear evidence surrounding the moderating effect of participant playfulness on intervention effectiveness. Our findings highlight the need for more rigorous quantitative assessment of play-related processes and health outcomes, and a clearer trait-state distinction when examining playfulness as an intervention outcome. We call for greater theoretical integration and a more holistic, developmentally-sensitive approach, emphasizing understanding boundary-crossing change mechanisms to harness play's transformative, therapeutic power for improving adult health and wellbeing. [ABSTRACT FROM AUTHOR]