Objective: To report on the role of nature in outdoor therapies through review and summary of existing systematic and meta-analytic reviews in an effort to articulate a theoretical framework for practice. Materials and methods: An umbrella review was conducted following systematic protocols PRISMA guidelines. Results: Fourteen studies met the inclusion criteria and represented five self-identified approaches: nature-based therapies, forest therapy, horticultural therapy, wilderness therapy, and adventure therapy. Clear and comprehensive descriptions of theory, program structure, and activity details with causal links to outcomes were mostly absent. Conclusions: A rigorous and determined program of research is required in order to explicit in-depth theories of change in outdoor therapies. Conversely, or maybe concurrently, a holistic theory of integrated relatedness may be developed as a parallel expression of support for nature in therapy while the explanatory science catches up.