Fast-paced city life could be giving you headaches and stress, but a new study suggests that it may be the air pollution, too. According to two new papers published in The BMJ, air pollution is linked to a higher risk of stroke and anxiety — mostly in developing countries.

In the first study the researchers, hailing from Edinburgh University, used a systematic review and meta-analysis to examine 103 observational studies spanning 28 different countries, focusing on the connection between short-term air pollution exposure and strokes. They analyzed the effects of carbon monoxide, sulphur dioxide, nitrogen dioxide and ozone, measuring particulate matter (PM), or the size of fine particles.

They found that when people were exposed to carbon monoxide, there was a 1.5 percent increased risk of stroke per 1 ppm, a 1.9 percent increased risk per 10 ppb of sulphur dioxide, and a 1.4 percent increase per 10 ppb for nitrogen dioxide. All of these pollutants were linked to an increased risk of stroke-related hospitalizations or deaths. This was especially true for low- to middle-income countries, while higher-income countries didn’t have as strong of an association.

Recent research has found that higher particulate matter in air pollution may result in a person’s neck arteries being narrowed, something that often occurs before stroke.

A second study completed at the Johns Hopkins University and Harvard University focused on the effect of air pollution on anxiety. They found that 15 percent of women experienced high anxiety symptoms, and this was linked to exposure to particulate matter; in addition, women living 50 to 200 meters away from a major road were more likely to have greater anxiety than women living farther than 200 meters.

It turns out that recent, short-term exposure has the biggest effect: the risk of stroke and anxiety increased during the first days or months that a person was exposed to air pollution.

The results of these studies “confirm the urgent need to manage air pollution globally as a cause of ill health,” Michael Brauer of the University of Columbia wrote in an accompanying editorial. Lessening “air pollution could be a cost effective way to reduce the large burden of disease from both stroke and poor mental health.”

Since the studies were observational, the researchers conclude that more research will be needed to substantiate them.