The most obvious benefit of having plants around the home is the aesthetic value they add; houseplants can help to bring character to a room, complement furnishings and create a sense of ‘homeliness’. But are there other benefits to keeping houseplants as well?

Various studies have suggested that being outdoors and experiencing nature can have a positive effect on mental wellbeing, helping to reduce stress, increase productivity and provide mental stimulation.

However, less research has been done on what impact plants can have on our health in an indoor setting. Most of the studies that have investigated the psychological effects of indoor plants seem to have focussed on their use in working environments, and what interactions with plants can do.

In this post, we’ll take a closer look at the existing research in more detail.

Defining ‘exposure’

A review of studies  from 2009, published in the Journal of Environmental Psychology,  analysed the current literature on this topic. From  a pool of research they highlighted the following results:

  • A 12% increase in reaction time from a group of students in a lab populated by plants compared to those without them. There was a systolic blood pressure change consistent with lower stress reactivity, faster stress recovery and higher reported attentiveness;
  • A 25% mean reduction in health and discomfort symptoms from a group of employees in the radiology department of a hospital after the introduction of 23 potted plants;
  • An overall significantly higher pain tolerance in women in an environment simulating a hospital waiting room, with 10 plants in the room compared to 0 in the control group;
  • And a large majority of 222 masters and graduate students and 28 teachers at a college reported a higher quality of air after potted plants were introduced after 30 days.

However the researchers had many reservations about the validity of these outcomes. They said it was hard to draw any concrete conclusions from these studies as ‘exposure’ to plants is a very loose term, and hard to define. The amount of time people actually spent noticing and engaging with the plant was difficult to measure.

Effect on heart rate

A more recent study from Chungnam National University in South Korea addressed this issue, by measuring cardiovascular changes when male adults directly tended to plants in an office environment.

An analysis of their heat rate showed a suppression of sympathetic activity in the autonomic nervous system (which deals with involuntary movements). They said this indicated relaxation of the muscles and the brain, suggesting a positive psychological effect.  

Effect on attention span

In another study, researchers from the Toyohashi University of Technology in Japan measured the effect of indoor plants on attention and meditation at different air temperature levels. The study also investigated the effect that plants had on several other types of tasks involving typing, maths and logic.

They concluded that the optimum temperature was between 22-25 degrees for the plants to have beneficial effects on attention useful enough to increase work performance.

So, while there is evidence to suggest that plants can have a calming effect and act as a form of stress relief in a working environment, it is inconclusive whether or not they are as effective without active engagement with them, or outside of a work setting.

Improving air quality

Aside from the physiological and psychological effect that indoor plants can have, an aspect of their function that cannot be disputed is their capacity to improve air quality.

Spending a lot of time indoors can lead to a condition called ‘sick building syndrome’, which causes headaches, nausea, sore and itchy eyes, and loss of concentration. This can be exacerbated by air conditioning and improved insulation.  

Furthermore, some household items such as furnishings, detergents and paint release volatile organic compounds (VOCs).

Some plants are thought to help to remove VOCs from the air. The RHS has a list of plants which they believe to be the most suitable for removing VOCs.

Plants also control humidity, which is important for our health as too much or too little of it increases the threat of contracting viral infections.

Lastly, plants absorb carbon dioxide and release oxygen into the atmosphere, which is perhaps their most well-known function.

There have been other experiments that claim that individual plants are particularly useful for certain purposes. For example, a study from the University of Northumbria claimed that rosemary can improve memory.

And lavender has been associated with helping insomnia by lowering heart rate and blood pressure (a point raised in the above-mentioned study from Chungnam National University).

What you can do

Whilst there is not sufficient evidence to suggest that populating your home with plants will definitely improve your mental and physical health, there is enough to suggest that having some around may be helpful; particularly  if you are creating a working environment.

Their capacity to remove carbon dioxide and VOCs from the atmosphere is an additional benefit that should help to make the air in a room cleaner.

But before going out and purchasing an array of plants, make sure you do some research.

Check the pollen count, especially if you suffer from allergic rhinitis (hay fever). High pollen plants could cause some discomfort to allergy sufferers. Another aspect to consider is the type of pollen in the plant you’re getting. Some people are affected more by trees, while others react to grasses or ragweed. If you have hay fever and are unsure about how a plant may affect you, or need further advice about managing your allergies, speak to your GP.