A small new international brain imaging study which looks at the brain activity of healthy volunteers from urban and rural areas, has found city living to be associated with increased response from the part of the brain called the amygdala, which is involved with emotional regulation and mood such as anxiety and fear.
The study authors noted that more than half of the world’s population now lives in cities and this makes the creation of a healthy urban environment a major policy priority and they also believe that cities have both health risks and benefits. According to projections by the United Nations, urbanization is picking up speed all over the world, with almost 70 percent of people expected to live in urban areas by 2050.
In the new study, the study authors investigated how human brain structures might be affected by urban living. Past studies have found that mood and anxiety disorders are more prevalent in city living: city dwellers are found to bear a 21% increased risk for developing anxiety disorders and a 39% increased risk for developing mood disorders and the incidence of schizophrenia is doubled among those born and raised in urban environments.
The new study was titled: “City living and urban upbringing affect neural social stress processing in humans” and was conducted by researchers at the University of Heidelberg and the Douglas Mental Health University Institute at McGill University. The new brain imaging study found for the first time the link between urban environment and the social stress processing part of the brain. In particular, the study researchers found that city living was associated with greater stress responses in the amygdala. In contrast, urban upbringing was found to be associated with activity in another part of the brain called the cingulate cortex, a region involved in regulation of stress.
In the new study, the study participants were divided into three categories: rural areas (populations less than 10,000), towns (populations between 10,000 and 100,000), and cities (populations greater than 100,000) and were asked to take a math face in order to put them under stressful conditions. They had to face time pressure and in some cases they were scolded through their headphones. The researchers found that the amygdala activity in the brain of the study participants increased as the population density where they come from increased. The new study suggests that there is a link between living in an urban environment and vulnerability to stress but it does NOT prove a cause and effect relationship.
According to Jens Pruessner, one of the co-authors of the new study, "when it comes to stress, it’s important to keep a balance” and he “suggests the need to keep things in balance, so after a period of working hard, you balance that with a period of off-time as well.”
Any danger perceived through the eyes or ears is transferred to the amygdala. This is an area of the brain that has to do with the processing of emotions. The images or sounds are processed by the amygdala, and when danger is perceived, a stress signal is then sent to the hypothalamus which forms part of the hypothalamic-pituitary-adrenal (HPA) axis responsible for the body’s automatic stress response system.
The HPA axis controls your body’s involuntary functions and includes aspects such as your heartbeat, breathing, and blood pressure. The HPA axis is also responsible for triggering the fight-or-flight response, thereby ensuring you have the energy and clarity of mind needed to deal with any danger perceived.
The adrenal glands are responsible for producing the hormones that put our body in this heightened state of awareness and readiness by producing adrenaline and cortisol. The process whereby the HPA axis reacts to stress is so fast that people are not aware of it.
Under normal conditions, people have no side effects when the body reacts in this way. The constant stress of city living, however, puts the body in a constant state of awareness and readiness by producing cortisol constantly and at elevated levels. The adrenal glands, after a while, start tiring out, and if corrective measures are not taken, goes into a crash mode with its associated complications, diabetes, heart problems, and depression being but a few. There are, however, a few measures city dwellers can put into place in order to get their cortisol production and stress levels under control.
