A study published by BMJ on March 24 suggests that air pollution can increase the clinical signs and symptoms of anxiety, regardless of existing comorbidities. The major observational study indicates that there is a 12-15 percent anxiety increase in individuals exposed to fine particle air pollution.

The research team, led by Melinda Power, ScD, postdoctoral fellow in epidemiology, John Hopkins Bloomberg School of Public Health, in Baltimore, Maryland, said, "Our study suggests that higher exposure to fine particulate matter, especially higher recent exposure, is associated with an increased risk of high symptoms of anxiety." Furthermore, another article also suggests that there is relationship between the occurrence of stroke and air pollution, specifically in developing countries.

The study was initiated by Power and her team, noting the potential significance of literature, suggesting the link between air pollution and mental health. They said that there is a lack of evidence suggesting the relationship between these two factors.

The research involved the examination of relevant data from the Nurse’s Health Study, which involved 71,271 women with an average age of 70. The study contained data, which summarises the valid estimates of the participants’ exposure to particulate matter in multiple occasions for an average of 15 years. In 2004, the researchers utilised the phobic anxiety subscale of the Crown-Crisp index to assess the prevalent symptoms of the participants. The assessment yielded that 15 percent of women scored six and above, which indicated severe anxiety.

There were no valuable information that indicates age, past history of anxiety, community status, residence in major roads, region of country and presence of comorbidities to strengthen the association between air pollution and present anxiety levels. Power further explains, "I think what I'd really emphasize is that this is an observational study, with very intriguing findings, but it definitely does need to be replicated in other settings and with other methods before we make any strong recommendations about what people should do to influence their anxiety levels.”

The University of Edinburgh in UK conducted a second study, which involved a meta-analysis and systematic review of 103 studies. The investigators of this study discovered that exposure to pollutants increases the risk of hospital admissions and death linked with stroke.

Specific data of the said study include: Carbon monoxide (1.5 percent increased risk per 1 ppm), sulphur dioxide (.9 percent per 10 ppb,), and nitrogen dioxide (1.4 percent per 10 ppb). Michael Brauer, ScD, MD, a professor at the School of Population and Public Health, University of British Columbia, Canada, shared in an editorial that, "the findings of these two studies support a sharper focus on air pollution as a leading global health concern."

Dr Brauer further writes, "The two linked papers in this issue confirm the urgent need to manage air pollution globally as a cause of ill health and offer the promise that reducing pollution could be a cost effective way to reduce the large burden of disease from both stroke and poor mental health."

Inflammation and oxidative stress are also believed by Power and Brauer to have a significant association with anxiety and air pollution exposure. "It's the most plausible pathway based on what we understand from how air pollution affects other organ systems. What we know is that air pollution affects the heart, and that seems to be via a pathway that involves inflammation," comments Brauer.

In conclusion, Brauer said that it is important to consider environmental risk factors as whole when studying mental disorders, such as anxiety. "The reason that air pollution may be important is not that it is likely to be a very strong risk factor for anxiety but that collectively, because everyone is exposed to air pollution, everyone has the potential to be affected by it," he said. Brauer closes by saying, "The flip side of that is that, if this really is a causal link, if you make improvements in air quality, there's a potential for really getting wide population benefits."

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