Dating back to the 1930s, researchers have discovered that mental illnesses are more common in densely populated cities than in greener and more rural areas, but it wasn't until recently that scientists have started to seriously study the mechanisms through which exposure to various environmental stressors could be wounding our mental health. Popular Science reports: Andreas Meyer-Lindenberg, director of the Central Institute of Mental Health in Mannheim, Germany, and his research partner Matilda van den Bosch, an environmental health researcher at the University of British Columbia in Vancouver, recently reviewed the scientific evidence for these and a number of other physical stressors to find out whether they contribute to depression. The pair searched for studies concerning a wide range of substances and situations that people might run across in everyday life. They discovered that while many of these factors were particularly abundant in cities, they weren't limited to urban environments. For example, air pollution isn't only found within city borders. Another potential danger was pesticides, which farm workers in particular come into contact with.
Still, a key part of improving our collective mental health will be making our cities more livable, says Meyer-Lindenberg. He and van den Bosch published their findings this year in the journal Annual Review of Public Health. More than half the world's population already lives in cities and this number is expected to rise to nearly 70 percent by 2050. In their review, Meyer-Lindenberg and van den Bosch found that some potential threats had been examined more thoroughly than others. For some, including pollen, there wasn't enough information yet to show a convincing link to depression. However, the team did find a number of studies suggesting that heavy metals like lead, pesticides, common chemicals like bisphenol A (BPA), and noise pollution may contribute to depression, although further research is still needed to confirm that this is the case. Even more compelling was the evidence condemning air pollution. In addition to causing respiratory and cardiovascular problems that kill millions of people each year, this particular menace raises our risk for a number of psychiatric problems. Poor air quality has been associated with depression, anxiety, and psychotic experiences such as paranoia and hearing voices. Obviously if you live in a city, these studies don't mean that you will develop depression or anxiety. Rather, they suggest that hazards like air pollution and pesticides will increase a person's overall risk, especially for those who are already vulnerable for other reasons.
"For people in poor communities, though, the impact is likely especially potent; not only does financial stress contribute to depression, but low-income neighborhoods face disproportionately high levels of air and noise pollution and lead exposure," the report adds. It goes on to say that people can fight back by spending more time in nature, which has been shown to calm activity in several brain regions involved in rumination, the tendency to obsess over one's mistakes and troubles that is a common feature of disorders like depression and anxiety.
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