Air Pollution Exposure Linked to Mental Health

Science is progressively demonstrating that genes have a significant role in an individual’s likelihood of getting depression. Additionally, researchers have discovered that when individuals with such genes are exposed to high amounts of air pollution, their risk of acquiring depression dramatically increases.

They discovered that exposure to air pollution altered brain circuitry in persons who were prone to depression. According to the latest study published in Proceedings of the National Academies of Sciences, these circuits are important for critical tasks related with depression, including as rational thinking and emotional processing.

“The critical discovery here is that air pollution does have an effect on our mental health,” Hao Yang Tan, MD, a Lieber Institute researcher and the study’s lead author, told Verywell. “And for individuals who are genetically predisposed, pollution’s effect on mental health and brain function is amplified.”

Yang Tan notes that, while experts have known for a long time that air pollution may contribute to mental illnesses, it was unclear how and why until now.

For a time, researchers debated whether air pollution caused depression neurologically or if it was a result of socioeconomic variables such as increased stress and physical sickness.

“We discover that air pollution affects the genes that control these brain functions, and that for people who have variants of these genes that predispose them to depression, air pollution has a much larger, magnified, multiplicative effect on these problem-solving and emotional control brain processes,” Yang Tan explained.

These findings contribute to how scientists and politicians around the world comprehend the extent to which air pollution affects our physical and mental health. And that’s why we need the best air purifiers out there to reduce the risk of depression.

The Link Between Depression and Pollution

Over 170 genes have been identified as being associated with an increased risk of developing depression. These genes, on the other hand, are activated and deactivated in response to environmental stimuli.

Which genes are activated and deactivated, when and for how long, all contribute to an individual’s “phenotype,” or observable characteristics.

It is not a guarantee that a genetic susceptibility to depression would result in the development of the disorder.

The neuroscientists from the Lieber Institute for Brain Development and Peking University in Beijing wanted to determine the extent to which air pollution, as an environmental element, impacts how genes express depression. They addressed this question with a combination of questionnaires, genetic investigations, and neuroimaging technology.

They began by studying a cohort of over 350 adults living in Beijing, one of the world’s most polluted cities. To begin, the researchers genetically analyzed the volunteers, determining their future risk of developing depression simply based on their DNA. They examined a total of 49 genes associated with depression.

Second, they gathered data on the amount of air pollution individuals had previously been exposed to. This was specifically accounted for in terms of what scientists refer to as particulate matter, which refers to tiny inhalable particles less than 2.5 microns in diameter, such as those found in automobile exhaust. They tracked this for six months previous to the trial, using data from nearby air pollution monitoring stations.

The individuals were then asked to complete cognitive tests while getting MRI scans to obtain a visual representation of which areas of the brain were most active and accountable for their performance during the exercises. Additionally, they received some unexpected negative comments during the exam to simulate stressful scenarios.

“We studied the neurological functions most closely associated with depression, specifically thinking and problem-solving functions, as well as all those that are dysfunctional in people who suffer from depression and are unable to concentrate, think clearly, or regulate their emotions,” Yang Tan explained.

The researchers next used brain imaging to determine how those 49 genes functioned in response to air pollution exposure.

“Given that this is the first study of its kind,” Jagdish Khubchandani, a public health professor at New Mexico State University who was not involved in the research, told Verywell. “The new aspect of this case is the brain imaging and the extensive testing. This is a monumental endeavor, and despite the tiny sample size in a local region, the sheer amount of tests and assessments make this study distinctive and warrants additional investigation.”

The findings indicated that those basic brain functions are actually altered in persons with a high genetic risk of depression and a high exposure to air pollution. As a result, depression was significantly more prevalent in individuals who already have that genetic propensity, particularly those exposed to high levels of air pollution.

“Aside from shortening lives due to lung cancer and heart attacks, air pollution may make life extremely uncomfortable for a large number of people,” Yang Tan explained.

The prefrontal cortex contains the same brain connections that are responsible for amplifying certain depression genes. This region of the brain is also involved in other mental disorders, suggesting that the effect of air pollution may be far broader.

“It seems likely that air pollution also has a direct effect on genes associated with these critical brain activities that are associated with not only depression, but possibly everyday living as well, as well as overlapping with other brain disorders,” Yang Tan said.

Smog in Our Brains

According to a new study, exposure to air pollution considerably increases the likelihood of acquiring severe mental diseases to the point where individuals may require hospitalization.

The connection between air pollution and decreased mental health is not novel. Increased exposure to air pollution has been associated with an increased risk of depression, anxiety, schizophrenia, personality disorders, and even suicide. Additionally, research indicates that exposure causes cognitive deficits in children’s development and, later in life, dementia.

What is alarming is the amount to which air pollution affects people’s mental health — to the extent that it increases the likelihood of hospitalization for mental illness by 18%, according to a new study published this month in the British Journal of Psychiatry. This figure refers to the risk associated with exposure to nitrogen dioxide (NO2).

The research, dubbed “the most thorough of its kind,” also indicates that even tiny increases in NO2 levels in the environment can result in a 32 percent increased chance of requiring outpatient mental health therapy. “You may observe this type of significant effect even at low levels of air pollution,” said Ioannis Bakolis, co-author of the study and a biostatistician and epidemiologist at King’s College, London.

The finding is troubling for India, where pollution levels are far from “low” — and contaminants encompass much more than NO2.

According to the WHO, India is home to nine of the world’s ten most polluted cities. Additionally, a 2020 study discovered that India’s outdoor air pollution levels are just as terrible in villages as they are in cities. According to a March study, worldwide air pollution levels decreased in 2020 as a result of the pandemic slowing the economy. However, as industrial activity resumes, emissions are returning to pre-Covid19 levels.

Air pollution has been linked to miscarriages, anemia, and even shorter lifespans in previous research – with India reporting the highest number of infant fatalities due to air pollution in the world in 2019. Air pollution has also been associated to increased Covid19 mortality rates in the aftermath of the global pandemic.

Additionally, NO2, whose primary source is car emissions, is increasing in India. According to a Greenpeace India report published in 2021, NO2 pollution surged in various state capitals between April 2020 and April 2021, with Delhi seeing a 125 percent rise, Bangalore experiencing a 90 percent increase, and Mumbai experiencing a 52 percent increase.

“Air pollution is adjustable, and on a large scale as well, by limiting exposure at the population level… We know there are treatments that can be utilized, such as increasing low-emission zones,” said Joanne Newbury, co-author of the study and a researcher at the University of Bristol who studies the impact of urban surroundings on people’s psychological health.

Experts advocate concentrating efforts on large-scale communal action to mitigate pollution’s impact.

“Individual-level mental health interventions are actually pretty challenging,” Newbury explained. Simultaneously, the researchers emphasized that “finding modifiable risk factors for illness severity and relapse could inform early intervention efforts and help alleviate the human suffering and significant economic costs associated with long-term chronic mental illness.”

What’s Next?

These types of findings could be beneficial to scientists and politicians worldwide. Densely populated metropolitan areas are particularly vulnerable to air pollution. These are also the areas with the highest levels of socioeconomic disparity.

“A lot of this work raises alarms and has been raising alarms for a long time,” Yang Tan explained. “Nearly 90% of the world’s population is exposed to unhygienic hair. As a result, it is pervasive. Climate change is a two-sided coin. As a result, it will remain with us for the foreseeable future.”

According to Yang Tan, researchers and policymakers must devise strategies to assist individuals during the time required to address these pollution challenges.

For instance, Yang Tan proposes that medical settings begin integrating genetic testing for depression in order to develop a profile of patients and assist in early intervention for those in need.

“With these genes, we may be able to develop drugs, vitamins, or other nutritional supplements that might help mitigate the effects of air pollution on some of these sensitive individuals,” Yang Tan explained.

In the future, Steven Pratt, MD, senior medical director at Magellan Health, who was not involved in the study, believes that duplicating this study with a more diverse sample size might be beneficial.

“Beijing has one of the greatest levels of air pollution in the world, and it is unknown to what extent we would see the same consequences with lower pollution levels,” Pratt told Verywell. “The substances that contribute to pollution in Beijing may differ from those in other cities.”

“At the societal level, we should address emissions as a matter of public policy,” Pratt continued. Employers, organizations, and building designers may all contribute by addressing indoor air quality through air exchange and filtration systems, Pratt advised, noting that these are the same adjustments employed to combat the epidemic.

“As we get a better understanding of mental disease, depression, and mental well-being, we see the importance of addressing whole-person solutions,” Pratt added. “It is not just about taking antidepressants or seeing a therapist; it is also about eating well, exercising, managing stress, maintaining social relationships, and, now, doing what we can to improve the quality of the air we breathe.”