Smartphone-based ecological momentary assessment reveals mental health benefits of birdlife

The main aim of the present study was to investigate the mental health benefits of encountering birds as part of everyday life. This was achieved using smartphone-based EMA, which allowed us to sample people’s experiences in real-time and real-world contexts.

Consistent with our first hypothesis, we found that participants’ mental wellbeing was significantly better when seeing or hearing birds compared to when not seeing or hearing birds. The effect was robust and observed at all three completion rate thresholds as well as after adjusting for potential sociodemographic confounders including age, gender, ethnicity, education and occupation. Interestingly, we found that the positive effect of seeing or hearing birds on mental wellbeing was more pronounced when individuals were outdoors (see Supplementary Table S8). People are most likely to see or hear birds in the context of green spaces, raising the possibility that the association between birdlife and mental wellbeing might in fact reflect an overall effect of nature on mental wellbeing. In order to minimise such possibility, we modelled seeing trees, plants, and seeing or hearing water as additional confounding variables. Critically, the results were still significant, providing support to a specific benefit of birdlife on mental wellbeing, above and beyond the well-established effect of green spaces.

Consistent with our second hypothesis, we found that the beneficial effect on mental wellbeing is still significant after the encounter with birds has taken place. This is consistent with our earlier research on the benefits of green10 and blue18 spaces which demonstrated time-lasting benefits for mental health. Perhaps unsurprisingly, the beneficial effect of seeing or hearing birds on mental wellbeing does wane over time. Specifically, it is reduced at the time of the first subsequent assessment following the encounter and is no longer significant at the time of the second subsequent assessment following the encounter. The use of an observational design meant that we were unable to establish causality in our findings. Nevertheless, we found that the association between seeing or hearing birds and mental wellbeing was still evident in the subsequent assessment, whereas mental wellbeing at a given timepoint did not increase the odds of seeing or hearing birds at subsequent timepoints (see Supplementary Tables S6, S7). This pattern of results could be an indication of a possible causal link effect of birdlife on mental wellbeing.

Consistent with our third hypothesis, the beneficial impact of everyday experience of birds on mental wellbeing was evident in both people with depression and people without a mental health condition. Once again, this finding was observed at all three completion rate thresholds as well as after adjusting for potential sociodemographic confounders including age, gender, ethnicity, education, occupation, seeing trees, plants and seeing or hearing water at the time of the assessment. Depression is the leading cause of disability and sick leave globally19, affecting an estimated 350 million people20. While antidepressant medication can lead to a significant reduction of symptoms12, there is an urgent need for non-pharmacological interventions to support mental health in people who have developed this illness. The current evidence for mental health benefits of green spaces in people with depression is mixed, with some studies reporting significant effects21,22,23 and other suggesting reduced benefits relative to healthy individuals24,25. Our investigation extends this existing literature by demonstrating that everyday experience of birdlife has beneficial effects not only in healthy individuals but also in people with a diagnosis of depression.

The potential policy implications of the present study are two-fold. First, the findings have implications for environmental and wildlife protection policy. The past few decades have seen a gradual but constant decline in biodiversity. A recent European report has revealed that there are 247 million fewer house sparrows and that one in six bird species have disappeared since the 1980s26. The reasons for this decline are complex. In rural areas, agricultural intensification and farming with chemicals are causing habitat loss and the disappearance of insects that feed birds; whereas in urban areas, bird population is falling due to a combination of trends including shortages of food, habitat loss, increase in diseases such as avian malaria and raising levels of air pollution. Our investigation provides support to the introduction of environmental and wildlife protection policies which encourage biodiverse habitats in urban, suburban and rural areas (e.g. permaculture farming, wilding initiatives, hedgerow and meadow enhancement, urban forestry). Second, the findings have implications for mental healthcare policy. In recent years social prescribing of nature-based activities, also known as “green prescribing”, has become increasingly popular to support individuals with mental illness including depression27,28. Our investigation supports the notion that visits to habitats with a high degree of birdlife, such as parks and canals, may be encouraged as part of green prescribing efforts.

Strengths

Previous studies examined the potential mental health benefits of birdlife using surveys or questionnaires requiring participants to recollect past experiences, or an artificial experimental setting involving the presentation of bird-related images or sounds to people sitting in front of a computer screen. In the present study, the use of EMAs allowed us to capture dynamic changes in the participants’ whereabouts and mental wellbeing in real-time and in real-world contexts. In particular we used smartphone-based EMAs, which provide more accurate and complete measurements when compared to the traditional method of paper diaries and stand-alone electronic devices29.

While the use of an observational design means that we cannot be certain that the observed increases in mental wellbeing are due to seeing or hearing birds alone, our analyses were adjusted for known sociodemographic confounders (age, gender, ethnicity, education, and occupation) as well as exposure to trees, plants, and water at the time of the assessment. In addition, the fact that the observed increases in mental wellbeing are still evident after the encounter with birds has taken place provides indirect support a potential causal link.

Limitations

The sample in this study was self-selected, recruited through a limited range of social media and websites. Furthermore, participants were aware of the fact that the study aimed to investigate the impact of the social and built environment on mental wellbeing, which may have made them more conscious about how they were feeling and bias their responses. While the 42-month recruitment timeframe allowed us to recruit a large sample, this occurred prior to and during the Covid-19 pandemic, which may have changed people’s stress levels and response to birdlife. Future studies should take potential effects of the pandemic into account. In addition, our sample still consisted primarily of white, university educated individuals based in the UK who were either in employment or education. Caution should hence be taken when applying the findings to the general population. Additionally, participants were asked to self-report whether they had ever been diagnosed with a mental health condition, and to indicate their diagnosis. Furthermore, while participants were allowed to select multiple diagnoses, the potential effects of comorbid diagnoses were not taken into account in the statistical analysis. Future studies would benefit from the use of validated clinical instruments to assess current symptoms and diagnosis, and the exploration of possible effects of comorbidity on findings. Finally, since we asked participants if they could see or hear birds, we were unable to dissociate between the potential mental health benefits of “seeing” and “hearing” birdlife. Nevertheless, in our encounters with birdlife, we do not perceive images and sounds of birds in a vacuum but as part of our multi-sensory experience. Therefore, it may be reductive to focus on visual and auditory aspects when assessing the mental health benefits of birdlife in real-time and real-world contexts. Consistent with this idea, a recent investigation suggests that the restorative potential of nature is greater when considering visual and auditory aspects together than when focussing on either modality separately30.

https://www.nature.com/articles/s41598-022-20207-6