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A study, and an accompanying article, published in PLOS Biology, report a possible link between exposure to environmental pollution and an increase in the prevalence of psychiatric disorders.
Dr Ioannis Bakolis, Lecturer in Biostatistics and Epidemiology, Institute of Psychiatry, Psychology and Neuroscience, King’s College London (IoPPN): said:
“The paper of Khan and colleagues provides a good overview of the shortcomings of both of the datasets. However, the conclusion that majority of the results are consistent across the datasets is highly debateable. In my view the press release does not reflect accurately the science and more attention should have being given to the concerns raised by the editor Prof Ioannidis in the response letter. Specifically, in relation to
“These findings add to the current evidence from previous studies of a possible link between air pollution and psychiatric disorders. Although there is emerging literature around the link of air pollution with depression, the link with bipolar and personality disorder is new. Although there are a few previous studies who provide similar results on the link between air pollution and psychiatric disorders it’s not really possible in studies like this which employ routinely collected data from registries to truly sort out what causes what. It’s easy to find coincidental changes in the environment at the same time that the number of people receive psychiatric diagnoses. The problem is that people who live in more polluted areas tend to be different from those who live in less polluted areas in many ways not caused by the pollution, and it could be that one or more of these other differences is the real cause of differences in rates of psychiatric disorders. Because of these issues about what causes what, no one study of this kind can, on its own, establish a causal link between a pollutant and its mental health consequences. Statistical adjustments made by the researchers to try to allow for these other differences were not adequate and some of the them were crudely estimated, especially in the US.
“There are numerous studies that have shown clear adverse health impacts of air pollution. World Health Organization (WHO) recommends that an annual target of 10μg/m³ would be best to protect people’s health while at the same time 91% of the world’s population lives in places where air quality exceeds WHO guideline limits. Few studies to date have tried to understand the dynamics of air pollution and their links with poor mental health so that public health researchers and policy makers can understand the societal and economic implications in order to intervene. This research could add more evidence, but in my view, we’re a very long way to appropriately quantify the effect of air pollution on poor mental health.
“There should be a special attention for innovative measures to improve air quality such as the introduction of the ultra-low emission zone (ULEZ) in London or boldly rethink the way that we plan our cities – some cities have announced car-free or car-less visions, including Milan, Copenhagen, Madrid and Paris and Oslo plans to ban all cars from its city centre permanently by 2019. Improving air quality is a tractable, though complex issue and therefore measures to reduce air pollution may represent a potentially impactful and rare primary health measure for the prevention of psychiatric disorders, although we still need to learn much more about if and how this would work.”
Dr Daniel Maughan, Associate Registrar for Sustainability at the Royal College of Psychiatrists, said:
“This paper builds on the increasing evidence of a link between air pollution and the development of mental illness.
“While the study does not show that air pollution causes mental illness, it does suggest that a strong link exists between early exposure to air pollution and an increased risk of developing several different mental illness including schizophrenia, bipolar, depression and personality disorder.
“However, there are many environmental factors which could contribute to poor mental health for those people living in areas of high pollution – such as population density and diminished access to green spaces – so it is therefore difficult to isolate poor air quality as the cause of mental illness.
“The College would welcome more research to help increase our understanding of how toxins in the air interact with the brain and how that could affect brain functioning.”
‘Environmental pollution is associated with increased risk of psychiatric disorders in the US and Denmark’ by Atif Khan et al. and ‘Air pollution as cause of mental disease: Appraisal of the evidence’ were published in PLOS Biology at 19:00 UK time on Tuesday 20th August.
DOI: https://doi.org/10.1371/journal.pbio.3000353
DOI: https://doi.org/10.1371/journal.pbio.3000370
Declared interests
Dr Daniel Maughan: No declarations of interest