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.