Any indoor gardener will tell you that growing houseplants does wonders for their psyche. Indeed, from a purely evolutionary perspective, it makes sense that living among greenery would improve our mental health: It assures us that our surroundings are home to a thriving ecosystem that can sustain our dietary needs. However, beyond this, is there any evidence that houseplants have a positive impact on mental health? Well, the scientific community answers with a resounding yes.
According to Han (2008), having somewhat visible plants in classrooms was correlated with higher student ratings of comfort and friendliness compared to control groups in high schools. Somewhat surprisingly, this study also found that the students in classrooms with indoor plants in them, students misbehaved less often. This corroborates existing research findings which suggest that the prevalence of trees in a landscape is negatively associated with crime rates, meaning in general, the more trees are present, the fewer crimes occur in the area (Troy et al., 2012). I personally have always been sceptical of this finding, because urban landscapes tend to have fewer trees. Urban populations are also denser, and people are exposed to more noise, stress and extreme poverty. Because of this, I have always taken this finding with a grain of salt. However, in the case of the Han study, these factors have been removed, but individual student differences were present. I would find it interesting to see if students’ misbehaviour rates could be accounted for by pre-testing or by peer/teacher questionnaires during the sampling process to see how plants would affect students who were repeat offenders who consistently get in trouble.
The presence of indoor plants also reduces stress and anxiety (Chang & Chen, 2005). Interestingly, physiological indicators os stress like EEGs and EMGs were used to measure stress and anxiety. Lowered autonomic responses measured by these devices will suggest that stress reduction is a result of physiological, objective reductions in stress levels, rather than subjective reporting of stress levels. This ability of plants to reduce stress may play a part in their popularity in urban environments, where people may not have gardens, or at least don’t have a great deal of space for gardening. Similarly, Berto (2005) suggests that the greenery and water in our environment signal to the brain that the environment is “restorative”, and thus, we can begin to replenish the neurotransmitters and other resources required for optimal psychological function. This makes sense because as I mentioned near the start of the post, the presence of plants and water suggests the immediate availability of the resources we need to survive.
And so, to you, I say: go out and buy plants! Don’t let anyone stop you. Feeling down? Get a new plant, water your plants, propagate! They call it horticultural therapy.