Researchers in the United States and China have discovered a curious link between air pollution and suicide rates.

China’s efforts to reduce air pollution have prevented 46,000 suicide deaths in the country over just five years, the researchers estimate.

The team used weather conditions to tease apart confounding factors affecting pollution and suicide rates, arriving at what they consider to be a truly causal connection.

The results in Nature Sustainability unearth air quality as a key factor influencing mental health.

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 co-lead author Tamma Carleton, an assistant professor at the University of California, Santa Barbara’s Bren School of Environmental Science & Management, knows these environmental factors can take a toll on mental health as well.

She’s previously studied the effect of temperature on suicide rates in India, finding that excessive heat drives those rates up. So she was curious when she 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 global average; two decades later it has fallen below that average, which itself is declining.

At the same time, air pollution levels were plummeting. “It’s very clear that the war on pollution in the last seven to eight years has led to unprecedented declines in pollution at a speed that we really haven’t seen anywhere else,” says Carleton. Perhaps these two phenomena were related, Carleton thought.

There are many reasons to control pollution around the world, and now suicide can be added to the conversation. 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.

Read the full article about air pollution and mental health by Harrison Tasoff at Futurity.