Home Mental Health & Well-Being Cleaner Air Significantly Reduces Suicide Rates, Reveals New Study

Cleaner Air Significantly Reduces Suicide Rates, Reveals New Study

Published: Last updated:
Reading Time: 5 minutes

Recent research published in the journal Nature Sustainability has revealed a significant correlation between improved air quality and a reduction in suicide rates in China. A collaborative team of researchers from various institutions used a sizable dataset and cutting-edge statistical techniques to isolate the effects of particulate matter (PM2.5) on suicide rates across Chinese counties from 2013–2017.

Suicide remains a critical public health issue globally, with over 700,000 deaths annually. In China, which accounts for 16% of global suicides, understanding the factors influencing suicide rates is essential. This study aimed to quantify the role of air quality improvements, particularly reductions in PM2.5, in the observed decline in suicide rates.

The researchers applied a statistical model that leveraged random increases in PM2.5 due to meteorological conditions. This model was matched with extensive data on suicide rates across Chinese counties. The approach allowed the researchers to estimate the causal impact of air pollution on suicide, considering both short-term and long-term effects.

The study found that a one-standard deviation increase in PM2.5 levels was associated with a 25% increase in weekly suicide rates. This effect was immediate, aligning with neurobiological evidence suggesting that PM2.5 can influence emotional regulation and impulsive behaviour. The study highlighted that the effects were particularly pronounced among women over 65, indicating a higher vulnerability in this demographic group.

China’s Air Pollution Action Plan (APPC-AP), implemented from 2013 to 2017, aimed to reduce PM2.5 levels in highly polluted regions. The study estimated that these improvements in air quality prevented approximately 45,970 suicides over the five-year period. The reductions in PM2.5 accounted for about 10% of the observed decline in suicide rates during this period.

Dr Tamma Carleton, an assistant professor at UC Santa Barbara’s Bren School of Environmental Science & Management, shared insights into the findings. She noted: “Issues like air pollution are often framed as a physical health problem leading to a spectrum of acute and chronic illnesses such as asthma, cardiovascular disease, and lung cancer. But these environmental factors can take a toll on mental health as well.”

Carleton had previously studied the effect of temperature on suicide rates in India, finding that excessive heat drives those rates up. “I was curious when I noticed the rate in China dropping far faster than its decline in the rest of the world. In 2000, the country’s per-capita suicide rate was higher than the global average; two decades later, it has fallen below that average, which itself is declining.”

The team faced a tricky task. “One of the bigger challenges with prior work on this problem is that air pollution is correlated with a lot of things,” Carleton explained. “For instance, economic activity, commuting patterns, and even industrial output correlate with pollution. And these activities can also affect suicide rates. Our goal was to isolate just the role of pollution in suicide as opposed to all the other things that might be correlated with air pollution.”

To this end, they took advantage of an atmospheric condition called an inversion, where warm air traps a layer of cold air beneath it like a lid on a pot. This can concentrate air pollution near the surface, leading to days with higher pollution levels that aren’t correlated with human activity. “This relatively random phenomenon enabled us to isolate the effects of air pollution on suicide rates,” Carleton said.

By decoupling pollution levels from human activity, which influences human behaviour, the authors believe they’ve truly identified a causal effect. The team compared suicide numbers across 600 counties between weeks with inversions and those with more typical weather, running the data through a statistical model. “Suicide rates increase substantially when air pollution rises,” the researchers found. The effect was particularly strong for elderly people, with older women 2.5 times more vulnerable than other groups.

Carleton added: “We aren’t certain why older women are especially vulnerable to this effect, though it may be partly cultural. Previous research suggests that most suicides by women in China are driven by acute crises. So if pollution has an acute effect on mental health, it could disproportionately impact older women.”

The phenomenon appears to happen relatively quickly. “Rates increase within the first week of exposure, and then abruptly decline once conditions improve. This suggests that pollution may have a direct neurologic effect, rather than creating chronic health issues that drive suicide rates up later on. Indeed, there is growing evidence that particulate pollution affects neurochemistry.”

Carleton emphasised the broader implications of the findings. “We often think about suicide and mental health as problems to be understood and solved at an individual level. This result points to the important role of public and environmental policy in mitigating mental health and suicide crises outside of individual-level intervention.”

She hopes the findings can reframe how society approaches suicide prevention. “Public policy about air pollution – something you can’t control, what’s outside your window – is affecting the likelihood that you take your own life. And I think that puts a different lens on the solutions we should be thinking about. It’s important that public health officials also know this as our climate gets warmer and pollution increases in many developing countries.”

The researchers noted significant regional variations in the impact of air quality improvements. The central and eastern regions of China, where PM2.5 declines were substantial, saw the highest number of prevented suicides. For instance, PM2.5 improvements in Pudong New District, a district of Shanghai, prevented an estimated 155 suicides, while in Binhai, a district of Tianjin, 122 suicides were prevented.

The study posits several mechanisms through which PM2.5 may influence suicide risk. One hypothesis is that particulate matter can affect brain function by modulating the release of neurotransmitters like serotonin, which plays a crucial role in mood regulation. Additionally, air pollution may impact physical health, leading to deteriorations in mental health and increased suicide risk.

The research also highlighted the role of acute exposure to high pollution levels, which can trigger impulsive and aggressive behaviour. This aligns with the findings that suicide rates respond quickly to increased PM2.5 levels, with no delayed effects observed in subsequent weeks.

While the study provides robust evidence linking air quality improvements to reduced suicide rates, it acknowledges several limitations. The data used did not cover all regions of China comprehensively, potentially leading to some mismeasurement. Additionally, the study could not directly identify the specific neurobiological mechanisms at play, highlighting the need for further research in this area.

Future studies could benefit from more granular, individual-level data to explore the precise pathways through which air pollution affects mental health. Moreover, extending the analysis to longer time periods could help understand the impacts of chronic pollution exposure on suicide rates.

Carleton plans to take a closer look at suicide rates in other Southeast Asian nations. Most suicide research has been conducted in the U.S. and Europe, she explained. It’s less clear what drives suicide in the developing world, which is also where we’re seeing the most rapid environmental change.

Of course, pollution is not the only factor that can lead a person to end their life. “About 10% of the overall decline over the past five years can be attributed to particulate pollution,” Carleton said. “That’s important, but it also leaves 90% unexplained by pollution.”

The findings underscore the importance of stringent air quality regulations not only for physical health but also for mental health. The significant number of suicides prevented by the APPC-AP suggests that pollution control policies can have profound public health benefits. These results add urgency to the calls for global action on air pollution, as improving air quality could yield substantial mental health gains.

China’s aggressive, successful policies achieved dramatic results in a short timeframe, serving as a potential model for other countries struggling with pollution and helping to reframe discussion about suicide in the modern world.

© Copyright 2014–2034 Psychreg Ltd