Now we finally know why so many city dwellers are depressed — and no, it’s not because of your failing local sports teams.

A new study from King’s College of London found that even tiny increases in vehicle emissions in highly polluted neighborhoods were correlated with shockingly high rates of clinical depression among residents — even when the researchers controlled for common environmental contributors to mental health conditions, like lack of access to mood-boosting green space or substandard housing.

Though all the regions the researchers studied had high rates of vehicle-related pollution, people who lived in neighborhoods that had just 3 micrograms of nitrogen dioxide more per cubic meter had a stunning 39 percent higher risk of a depression diagnosis, when compared with the residents of neighborhoods with the lowest levels of NO2, which is commonly found in diesel exhaust emitted by heavy trucks.

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