Examining the link between air pollution, green space and depression

In a recent LongITools study, led by the Amsterdam University Medical Centers, researchers explored the links between air pollution, access to green spaces, and depressive symptoms. By examining four population ‘cohorts’ in the UK and the Netherlands, researchers discovered that higher air pollution was linked with depressive symptoms in two of the groups. Additionally, in one cohort, greater exposure to green spaces was associated with fewer depressive symptoms. The paper, published in Environmental Research, could provide a direction for future research into the effect our environment can have on our mental health.

Why was a new study necessary?

Depression affects almost 280 million people worldwide. Although there are now effective treatments – such as cognitive behavioural therapy and antidepressant medication – the prevalence of depression has increased worldwide in the last twenty years.

The link between air pollution and depressive symptoms has been examined. Recent reviews have found an association between fine particulate matter of 2.5μm or less in diameter (known as PM_2.5) and nitrogen dioxide (NO₂) with the symptoms of depression. Previous research has also shown that access to green space is linked with lower depressive symptoms. However, past studies tend to measure depressive symptoms at one fixed point in time. As such, we know little about how these environmental exposures impact depression over longer periods.

The study aimed to address this by tracking depressive symptoms at multiple junctions in an individual’s life. This allowed researchers to see if exposure to air pollution or green space could affect depressive symptoms for an extended period, helping inform our understanding of how our environment influences our health.

What was done and what did we find?

The study gathered data from almost 25,000 adults from four cohorts, in the UK and the Netherlands.

Researchers used participant questionnaires, Europe-wide data on air pollution and home addresses’ proximity to green space using NDVI (normalised difference vegetation index) satellite data. Several other variables that could influence their findings – such as sex, education levels, the levels of deprivation in an area, and their ‘moving status’ (if they’d relocated after their first baseline assessment) were also considered.

“The findings demonstrated that, in two cohorts, depressive symptoms were higher in those with greater exposure to air pollution, specifically PM_2.5. This is in line with past literature on the subject and other previous studies which have identified a positive link between fine particles and depression. Additionally, in one Dutch cohort, greater green space exposure was linked to lower depressive symptoms. There was no strong evidence, however, for environmental exposures modifying depressive symptoms over time.”
Irina Motoc, first author.

Additionally, LongITools researchers found that depressive symptoms in general increased with age, regardless of the individual’s exposure to pollution or green spaces. As such, the protective effect of green space on depressive symptoms weakened slightly over time in one of the cohorts.

Ultimately, the associations assessed by the study between air pollution, depressive symptoms and green spaces were inconsistent across all cohorts. Some exposures seemed to be associated with depressive symptoms in certain groups, but not others; this could suggest strong variability in how these environmental exposures affect individuals in different populations and across ages, with the baseline ages and age ranges being different in all four cohorts.

It is important to note that, as this study was purely observational, it cannot prove any causal link between air pollution and depressive symptoms in adults. However, it does provide a direction for future research – where the link between what we breathe, our access to green spaces, and our mental health can be explored in greater depth.

For further information, please contact:

Associate Professor Susanne R. de Rooij, Amsterdam University Medical Centers.

Paper

Irina Motoc, Bigina N.R. Ginos, Ana Goncalves Soares, Ahmed Elhakeem, Trudy Voortman, Maryam Kavousi, Annemarie I. Luik, Tessa J. Roseboom, Susanne R. de Rooij. Examining associations of air pollution and green space with depressive symptoms in adults: A LongITools cross-cohort analysis. Environmental Research, Volume 261, part 1, (2025).