Thursday June 23 2011
Mental health issues are more common in city dwellers
People who live in the country are happier, according to the Daily Mail. The article said: “city dwellers think differently from people who live in the country – and are more likely to suffer mental illness as a result.”
The news is based on German research that compared patterns of brain activity seen in response to social stress in urban and rural dwellers. The study’s authors say previous studies have shown that mental health issues, such as schizophrenia, anxiety and mood disorders, are generally more common in people who live in or grow up in cities. To test this theory, the researchers exposed volunteers to negative verbal messages and asked them to complete puzzles while having their brains scanned. The study found that city dwellers had greater activity in certain areas of the brain involved in negative mood and stress.
However, the study’s results should be viewed in context. The study did not assess the participants’ happiness or general stress levels, the brain activity seen does not necessarily equate to a higher risk of mental illness, and the negative messages used do not necessarily represent real-life situations. Further research will be needed to discover the precise mechanisms through which urban living might affect mental disorders.
Where did the story come from?
The study was carried out by researchers from the University of Heidelberg in Germany and McGill University in Canada. The research was funded by the European Community’s Seventh Framework Programme, the German Research Foundation and the German Federal Ministry of Education and Research.
The study was published in the peer-reviewed scientific journal Nature.
The findings of this study were generally misinterpreted by the media. Many news sources implied that researchers had found that urban environments actively cause mental illness. This study’s design is not capable of proving causal relationships, but can only describe associations between different factors.
In addition, the study did not measure relative levels of stress in urban and rural settings, and none of the study participants had a mental illness. The Daily Mail reported that rural residents were “happier”. However, this conclusion is not supported by this research, which did not measure or investigate happiness in urban or rural dwellers. The Guardian, however, accurately represented both the study’s findings and limitations that mean it cannot prove causality.
What kind of research was this?
The authors of the study reported that previous epidemiological studies have shown urban residents to have a higher risk of many psychological disorders, including depression, schizophrenia and anxiety disorders. This series of small cross-sectional studies explored this theory by comparing the impact that social stress has on the brain activity of urban and rural residents.
While several characteristics of the relationship between urban living and the prevalence of mental illness support the theory that city living may directly influence mental health, this has not been conclusively shown. For example, it is not understood how urban living might have this effect. This study investigated how people process social stress, one potential mechanism through which urban living might affect metal health.
Although this study’s design allowed the researchers to identify differences in how urban and rural residents processed simulated social stress, it couldn’t determine whether urban living caused these differences. Also, as mental health outcomes were not assessed in this study, it cannot tell us whether any differences found might affect mental health over time.
What did the research involve?
Researchers carried out a series of three experiments which examined the impact of social stress on brain activity in individuals living in rural settings, small towns and urban areas. The first experiment exposed the individuals to stress by requiring them to solve arithmetic problems under time pressure and receiving negative feedback from investigators between tests through headphones. Stress levels were assessed by measuring levels of the hormone cortisol, and the participants’ heart rate and blood pressure. Individuals completed the tasks while undergoing a brain-scanning procedure called functional magnetic resonance imaging (fMRI), which is capable of detecting the activity occurring in each region of the brain. Researchers compared the patterns of brain activity in rural, small-town and urban dwellers, as well as those who were raised in urban and other settings.
The second experiment used a different problem-solving test under similar social stress conditions (continuous negative feedback through video), and recorded and analysed brain activity in the same manner. The final control experiment carried out another series of problem-solving tests but without any social stress conditions, in order to be sure that brain-activity patterns were due to the stress-inducing interventions and not the test itself.
The first experiment included 32 people, the second 23 people, and the third 37 people. None of the participants had a mental illnesses or a high risk of mental illness.
What were the basic results?
Across all the experiments, the same patterns of brain activity emerged, with several regions of the brain consistently activated during social stress situations:
- Current city living was associated with activity in the amygdala, a region of the brain that signals negative emotions and environmental threats. This area has also been suggested to play an important role in anxiety disorders, depression and violent behaviour. Amygdala activity was highest in city dwellers, followed by town dwellers and finally rural residents.
- Urban upbringing was associated with increased activity in another area of the brain that is reported to be a key regulator of negative mood and stress. The level of activity was greater with more exposure to urban upbringing.
How did the researchers interpret the results?
The researchers concluded that the association between current city living and increased activity in the amygdala was supported by previous epidemiological research findings.
While the study found that there was increased activation within specific brain regions in response to social stress, the researchers say that this cannot be directly linked to psychological disorders without confirmation through further research. Importantly, they point out that their study did not look at the impact of stress on brain activity in individuals with mental illness.
This study examined the activity of specific brain regions in response to simulated social stress. It found that brain activity differed between individuals raised in or living in urban areas and rural dwellers.
However, the study’s design means that it cannot determine why these differences in brain activity occurred, nor whether the differences are linked to mental health problems or stress in real-life situations (as some newspapers implied).This study has further limitations:
- It was not able to confirm whether the observed brain differences existed in individuals before they came to live in cities.
- Only a small number of people took part in all the experiments. Therefore, the results should be interpreted cautiously, as a small sample size increases the uncertainty of the findings.
- Individuals participating in the study were healthy volunteers from Germany, and grew up and lived in a relatively safe and prosperous country. It may not be appropriate to apply the results to other settings.
- The stress-inducing factor in this experiment was only a model that approximated stressful social interactions. However, it is debatable how closely it represents specific environments or momentary social interactions in the real world.
Discovering underlying social mechanisms that might cause the higher rates of schizophrenia, anxiety and mood disorders observed in urban residents could have important implications for healthcare and patient wellbeing. However, although this research provides a valuable insight into possible interactions between a stressful environment and neurological processes, it cannot confirm that this actively leads to mental health problems. The current research does not provide sufficient evidence to inform any policy decisions at this time.