This study aims to provide foundational data for developing forest therapy programs to improve mental health conditions by reviewing program development studies, casebooks published by governmental organizations, and existing programs conducted in forest therapy settings and analyzing the status and activities of programs from various disciplines in Korea and abroad. During the collection phase of mental health improvement programs, studies that were not related to depression, anxiety, or stress, or were not relevant to program development, were excluded. Additionally, studies that did not include detailed program plans were omitted from the activity analysis. The literature review focused on academic articles and theses published between 1990 and 2023, identifying 403 relevant studies. Casebooks were collected from three domains, while forest therapy programs were obtained from three forest welfare organizations. These programs were categorized/analyzed based on their general characteristics, structure, and activity content. The findings indicated that research on psychotherapy (forest therapy) programs peaked between 2010 and 2014 (2020 and 2023) in casebooks and field settings. Programs documented in the literature commonly involved 11-20 sessions lasting 60-90 min, whereas casebooks and field programs typically featured fewer than five sessions, each lasting over 180 min. Nineteen purpose-driven and 40 practical activities were identified, providing a theoretical basis for developing forest therapy programs tailored toward alleviating depression, anxiety, and stress. The proposed activities and elements can support the diversification and professionalization of forest therapy programs, fostering more effective and specialized approaches to improve mental health.