Trees, good for the spirit (and the mind…)

Do trees make us happier?
Image: Florian Hirzinger/Wikimedia Commons.
Image: Florian Hirzinger/Wikimedia Commons.

For those who don’t subscribe to more formal organised religions, with their attendant man-made paraphernalia and iconic places of worship (such as churches and cathedrals in the Christian tradition), forests are often viewed as nature’s own cathedrals, thereby helping to provide for Man’s spiritual well-being or wellness. A study by Mark Taylor et al. provides evidence that those natural cathedral’s individual units of construction – i.e. the trees – can also provide for humankind’s more cerebral medical needs. In their analysis of secondary data sources, they consider the issue of ‘street trees in the nature-health nexus’ by examining the association between the density of street trees in London (UK) boroughs and the rates of antidepressant prescribingDepression is ‘a state of low mood and aversion to activity that can affect a person’s thoughts, behavior, feelings and sense of well-being’. It is a serious, global health issue that contributes to the loss of 11.3 million working days in the UK alone, and may be treated with medication, so-called antidepressants. So much for the background to the investigation; what did they find? The team found a decrease of 1.18 prescriptions per thousand population per unit increase in trees per kilometre of street, suggesting that trees in the street may be a positive urban asset to decrease the risk of negative mental health outcomes*. I don’t suppose an alternative interpretation is that tree-lined urban areas are likely to be the more affluent ones, and maybe such high-worth individuals seek remedies from private medical practitioners (whose prescriptions are excluded from the analysis) or have ‘non-prescription’ methods of coping with any depression? Or, perhaps, the comparatively well-off residents therein might not be so prone to illnesses, whether depressive or otherwise…? Nevertheless, and as the authors recognise, although this brief report is one of association and not – necessarily… – of causation, it does suggest a link between greenery in the environment and enhanced mental health/well-being, and is in keeping with a more general debate about the value of ‘nature’ and public health. If, however, presence of an ‘urban forest’ of trees is not enough to repress or suppress any depressive tendencies, then one could consider an ancient Amazonian rainforest remedy, ayahuasca. As ‘a psychedelic brew made out of Banisteriopsis caapi vine’ (which has an intimate association with trees that they often exploit for support) often in combination with various other plants (such as Psychotria viridis, a shrub – which is a small version of a tree), ayahuasca has been anecdotally promoted as a treatment for depression. However, evidence-based clinical studies of its benefits in this regard are rare. But a pilot study by Flávia de L. Osório et al. of six volunteers in an inpatient psychiatric unit gives cause for hope that ayahuasca has antidepressant effects. Although a sample size of six may be the magic number for use of appropriate statistical tests, further trials on larger numbers of participants will be needed to establish the true potential for use of ayahuasca in this way **. Nonetheless, it’s a start, and cause for cautious optimism. But, lest you be tempted to experiment with self-administration of the remedy, be warned: one of the major ingredients in the concoction is DMT (N,N-Dimethyltryptamine), a psychedelic compound that has Class A drug status in the UK and whose use is therefore illegal (as is also the case in several other states in the world). So, ayuahasca’s unapproved, albeit ‘experimental’, use could result in a jail term***, which, in an ironic way, is probably enough to make the most robust of individuals ‘depressed’, which sort of gets us back to where we began this news item(!).

* But if you do need a prescription for medicines, you can still thank a tree for providing the paper upon which your prescription is written/printed!

** One can only trust that any modern-day use of volunteers for trials of ayahuasca doesn’t achieve the same degree of notoriety and unintended consequences as attributed to similar invitations to test LSD in the USA in the 1950s and 1960s.

*** Unless you can defend your use of ayahuasca on religious grounds(!).