When we're freaking out, we can always count on a few deep breaths to help us calm down. But, new research suggests the air we breathe might actually be making us even more stressed out. The study, published online this week in the BMJ, looked at data from 71,271 women in the Nurses' Health Study. The data (beginning in 1988) included where people lived, how much particulate matter they had been exposed to in their environment, and their anxiety symptoms. Overall, the results showed that 15% of the women in the sample reported having high anxiety symptoms, such as unreasonable fears of heights, crowds, or traveling by bus. The women's levels of exposure to a certain kind of particulate were associated with a higher risk of reporting anxiety symptoms. And, the results suggested that recent exposure to particulate matter (within a month before the anxiety assessment) may have had more of an impact than earlier exposures. Of course, just because these two things are correlated doesn't mean the air quality is causing the anxiety. One possible complicating factor is that living in cities big enough to have a problem with air pollution may also be inherently stressful in other ways (ugh, traffic). Or, air pollution may cause other health issues that, in turn, increase our anxiety levels. Because smog exposure has been associated with other physical health factors (such as heart disease), it wouldn't really be surprising if it had an effect on our mental health as well. And, previous studies have shown a similar connection between pollution and mood disorders. Stress can be such a nasty thing in so many ways, we really didn't need another source of it. But, thankfully, we have plenty of ways to get rid of it, smog or shine.