Forest therapy is an emerging holistic health practice that uses multisensory immersive engagements in forest settings to achieve health and wellbeing outcomes. Many forest therapy engagements take place via slow walks along a trail to optimally experience the array of sensory phenomena afforded along the route, yet surprisingly few forest therapy studies to date have investigated the characteristics of forest sites and trails that give rise to healthful experiences. In this research, we employ a hybrid approach to understand the conditions and features that contribute to a good forest therapy trail, using interviews with forest therapy guides to identify and highlight concepts for further refinement and structuring via a broad, integrative review of the relevant research and planning literature. Through this iterative approach, we identify and describe three site-related criteria (landscape character and quality, tranquility, and accessibility) and two trail-related criteria (design and construction and key features and qualities), each with a number of sub-criteria detailing specific conditions and considerations. This effort helps build a conceptual foundation and evidence base for assessment procedures that can be used to identify existing trails and design new ones that meet the needs of forest planners, managers, guides, and participants for the growing international practice of forest therapy.

While most definitions of forest therapy emphasize the role of multisensory, immersive experiences in nature to achieve human health and wellbeing outcomes, reviews of research on forest therapy to date have predominantly focused on outcomes and provide limited insight on the factors and conditions that give rise to nature experiences. In this scoping review we employ a conceptual framework developed in the context of landscape perception research to examine empirical studies of forest therapy in terms of how the fuller process of human, forest, interaction, and outcome components are conceptualized and measured. Our literature search identified 266 studies focused on forest therapy and related activities, which were coded on a number of variables related to each of the four components in our framework. While most studies reported positive mental and/or physiological health outcomes using a wide array of measures, the typical study used small, homogeneous samples of participants who engaged in limited interactions with a forest environment that was minimally described. However, our analysis also identified a wider range of findings with regard to human-forest interactions, which together provide important insights for guiding forest therapy research and the provision of forest therapy trails, settings, and programs.