Environmental preference might mediate the benefits of nature-based therapies

The benefits of psychotherapies are highly variable between patients, perhaps most notably because of personality types, cultural background and one's conception of mental ill health, among others.¹ Case in point, many patients consider group psychotherapy unacceptable and others do not consider psychotherapy credible at all. Similar variations are surely also implicated in nature-based therapies (NBTs).

For example, in the first instance, evidence over recent years has increasingly pointed to a benefit to mental health outcomes from exposure to and use of natural environments, commonly conceived in the literature as ‘urban green spaces’. The causal mechanisms are complex, but usually distilled to: improved exercise and socialisation opportunities, reduced exposure to air and noise pollution, and importantly for NBTs, psychological stress-reduction and attention restoration.² As well as being evidenced, it is easy to anecdotally see how these non-psychotherapeutic components of NBT – the simple exposure and interaction with one's natural environment – are mediated culturally, and also by personality and personal environmental preferences inter alia. Between cultures, for example, there is dramatic variation in perceptions of natural environments and understandings of appropriate uses of these spaces.³ These variations are likely to modulate the causal mechanisms of the green space–mental health benefit.

Second, it is reasonable to suggest that these variations in the perceptions of natural environments affect the acceptability, credibility and therefore adherence and completion rates for NBTs. Until now the evidence for green space benefit to mental health outcomes has come largely from observational studies, which demonstrated varied effect sizes, and suggested differences as a result of the quality of environments, perceived safety concerns, among other individual personality and community factors.⁴

Stigsdotter and colleagues’ most recent report therefore, which demonstrates non-inferiority of one particular brand of NBT for stress-related mental illnesses compared with a more mainstream cognitive–behavioural therapy, is to be welcomed.⁵ Although, of course, randomisation of patients is an essential facet in the production of reliable and valid science, this may have masked a subpopulation with complementary personalities and cultural characteristics (etc) for NBTs. And as the authors allude, given equal study withdrawal rates after randomisation, there may well be an equal subpopulation with preference for office-based cognitive–behavioural therapy (perhaps for perceived credibility reasons). The non-inferiority demonstrated in this trial therefore gives us the option that those patients who may be open and keen on the idea of NBTs may be more adherent, more likely to complete the intervention and independently receive greater benefit through the causal mechanisms described above. NBTs therefore might now be considered another option (rather than any kind of replacement) in the tool kit of primary care or mental health services aimed at addressing the high burden of stress morbidity, especially for those expressing a preference for it.