Strengths and Limitations
To enhance the methodological quality and evidence, while decreasing the risk of bias, as required in reviews on the topic of forest therapy [Nature relatedness in the ANKER-Study was assessed via three questionnaires (Connectedness to Nature Scale, Inclusion to Nature Scale and Nature Relatedness Scale). The results indicated that connectedness to nature is a stable personality characteristic, as the scores changed only slightly, even though significance occurred over time, i.e., low clinical significance can be expected. Furthermore, it could be assumed that there was a selection bias in the present study population, because especially persons with a high affinity to nature would volunteer to participate in such a study design, which is also reflected in the high, stable values of these three questionnaires. As the bootstrap sample size simulation based on the results of the ANKER study shows, a sample size of n ≥ 80 persons is recommended in order to similarly match the psychological and physiological parameters of nature-based interventions. Although, in this study only about half of the recommended subjects participated, significant results could be obtained already, therefore higher case numbers are likely to generate even clearer and clinically more relevant results. Additionally, further research specific to women with regard to mountain hiking and also forest therapy should be conducted to further elucidate the effects of these interventions on female gender and to ascertain their backgrounds, e.g., fears related to visiting the forest [Buckley and Brough [