Doctor’s orders: Does air pollution cause depression?

Inversion settles into Utah Valley 05

An inversion, created from a top layer of warm air that keeps pollutants trapped in the cold air beneath, hangs over the Lake Mountain area of Utah County on Saturday, Dec. 9, 2017, as seen from Point of the Mountain in Lehi. Isaac Hale, Daily Herald

I saw someone ask this question the other day online. Does air pollution cause depression? Or if you already have depression, can it make it worse?

Now that February is ending, and the weather is warming up, we will all start coming out of those winter “blahs.” Around March every year I seem to suddenly just start feeling happier and more cheerful. A lot of that can be from the sunshine — Vitamin D can definitely make a difference to my mood. Having longer days and not having to wear lots of layers probably boosts my mood too. No one likes driving to and from work in the dark. But could our winter inversions also be having an impact?

The answer is: It depends. Sorry. I know that isn’t very satisfying. Some studies, including a rather large one in Europe (Zijlema et al. 2016), didn’t find a relationship. Others found a relationship that is quite strong. Why might different groups show different results?

The issue is that depression is complicated. It involves genetic, social, behavioral and environmental factors. Some people may have depressive symptoms mostly because of genetics. Another may be experiencing depression after a trauma. While yet another person may have depression because of a mix of factors, including being more susceptible to the influence of air pollution.

There are also aspects of someone’s life that can help reduce their risk of depression, like good diet and exercise, sleep, reduced stress, and having a supportive network of friends and family. One study in China (Wang et al. 2018) suggested that having good “social capital” in a neighborhood actually mitigated the influence of air pollution on depression. Social capital is basically a measure of community trust and how people relate to each other in a society. Feeling included in a tight-knit community is certainly a protective factor against depression brought on by a variety of circumstances.

A specific type of air pollution called small particulate matter (abbreviated PM2.5) is known to increase risk for a host of respiratory, cardiovascular and even neurological conditions. One aspect of PM2.5 that is especially interesting is that it can stay in your system and build up. In a large analysis of many studies on air pollution and depression, another research group (Gu et al. 2019) found that being exposed to PM2.5 over time can increase your risk of depression.

In Utah we have a special type of air pollution: inversion. We don’t know as much about the direct effect of the inversion period on depression symptoms on society as a whole.

The studies that have been done suggest that there is a connection, but we need to know more. Since inversions happen in the winter, when there is less sunlight and more infectious diseases, it can be hard to tell the different causes of depression apart. There are scientists in Utah and elsewhere around the world working to understand the relationship at a deeper level.

Depression and inversions is a great example of a health relationship that may well be there, but we just need to do a little more work. In the meantime, reducing air pollution remains one of the top health priorities in Utah. Health is strongly impacted at all ages by the particulates we breathe in every day. Remember to buy gasoline at stations that sell low-emissions Tier 3 gasoline (find the one closes to you at tier3gas.org), chain trips together, and be idle free.

Dr. Chantel Sloan is an associated professor in Brigham Young University’s Department of Health Science. She received a Doctorate in Philosophy and Genetics at Dartmouth College and completed a postdoctoral program at Vanderbilt University Medical Center.

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