In 1965, health authorities in Camberwell, a bustling quarter of London's southward sprawl, began an unusual tally. They started to keep case records for every person in the area who was diagnosed with schizophrenia, depression, bipolar disorder or any other psychiatric condition. Decades later, when psychiatrists looked back across the data, they saw a surprising trend: the incidence of schizophrenia had more or less doubled, from around 11 per 100,000 inhabitants per year in 1965 to 23 per 100,000 in 1997 — a period when there was no such rise in the general population (J. Boydell et al. Br. J. Psychiatry 182, 45–49; 2003). The result raised a question in many researchers' minds: could the stress of city life be increasing the risk of schizophrenia and other mental-health disorders?
nature.com/stress
The question is an urgent one. Back in 1950, less than one-third of the world's population lived in cities. Now, lured by the prospect of work and opportunity, more than half do. Mental illnesses already comprise the world's biggest disease burden after infectious diseases and, although global statistics do not yet show any major increase in incidence, the cost is rising. In Germany, the number of sick days taken for psychiatric ailments doubled between 2000 and 2010; in North America, up to 40% of disability claims for work absence are related to depression, according to some estimates. “It seems that cities may be making us sick,” says Jane Boydell at the Institute of Psychiatry in London, who led the Camberwell study.
Anecdotally, the link between cities, stress and mental health makes sense. Psychiatrists know that stress can trigger mental disorders — and modern city life is widely perceived as stressful. City dwellers typically face more noise, more crime, more slums and more people jostling on the streets than do those outside urban areas. Those who have jobs complain of growing demands on them in the workplace, where they are expected to do much more in less time.
But the idea has not been widely tested. It is difficult to study whether something as complex as a 'city environment' has an impact on the brain. To complicate matters, many growing cities include immigrant populations, which already have an increased risk of psychiatric disease associated with social isolation.
Alison Abbott talks about stress and city living.
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Now, a few scientists are tackling the question head on, using functional brain imaging and digital monitoring to see how people living in cities and rural areas differ in the way that their brains process stressful situations. “Yes, city-stress is a big, messy concept, but I believed it should be possible to at least see if brains of city-dwellers looked somehow different,” says Andreas Meyer-Lindenberg, director of the Central Institute for Mental Health in Mannheim, Germany. And if scientists can work out what aspects of the city are the most stressful, the findings might even help to improve the design of urban areas. “Everyone wants the city to be beautiful but no-one knows what that means,” says Meyer-Lindenberg. Wider streets? Taller buildings? More trees? “Architects theorize a lot, but this type of project could deliver a scientific basis for a city code.”
Relentless stress
Considered from an evolutionary standpoint, the physiological stress response is definitely a good thing: it helps mammals to survive. Any threat, whether from a predator, dwindling food supplies or an aggressive enemy, triggers release of hormones such as cortisol and adrenaline. These hormones raise levels of sugar in the blood and redistribute blood flow to muscles and lungs, so that animals can respond to the threat by running, hunting or fighting.
“This type of project could deliver a scientific basis for a city code.”
Problems arise when the stress response doesn't switch off. Stress-hormone levels that stay too high for too long cause high blood pressure and suppress the immune system. And, although the mechanisms are unknown, scientists agree that severe or prolonged stress also raise the risk of psychiatric disease — most brutally in those who have a genetic predisposition, and when the stress occurs while the brain is still developing. In theory, then, the ceaseless challenges of the city could produce this kind of damaging stress. Some fear that they could end up driving an increase in mental illness around the world.
The only signs of an increase, however, come from relatively small, local studies. “It's frustrating — we feel it should be rising,” says Ronald Kessler, a mental-health epidemiologist at Harvard Medical School in Boston, Massachusetts. “But globally we have not seen this, and there are also studies which indicate it isn't even rising in cities.” However, reliable data on the prevalence of psychiatric disease are hard to find because diagnoses are often imprecise or incompletely recorded. The Camberwell study was influential because, unusually, it captured all those who were diagnosed with a mental disorder, even if they were not admitted to hospitals, and the researchers involved carefully reviewed every case.
Published in 2003, the Camberwell study deeply impressed Meyer-Lindenberg, who was then at the US National Institute for Mental Health in Bethesda, Maryland, researching how genetic risk factors for schizophrenia affect brain function. As a student in Manhattan some years earlier, Meyer-Lindenberg says, “I had been struck by the number of homeless mentally ill people on the streets, and the problems of the city somehow resonated with me”. He wondered if city living was somehow making the brain more susceptible to mental-health conditions. When he returned to his native Germany in 2007, he decided to tackle the question directly. But at the time, Meyer-Lindenberg says, “people said the effect would be too subtle to make sense of”.
Yet the results of his study, published last year in Nature (F. Lederbogen et al. Nature 474, 498–501; 2011), clearly showed that people who grow up in cities process negative emotions such as stress differently from those who move to the city as adults. His team scanned the brains of 55 healthy volunteers as they carried out arithmetic tasks under a constant bombardment of negative social feedback. “We'd always let them know through headphones that we thought they were failing, or at least not doing as well as other subjects we'd had in the scanner,” says Meyer-Lindenberg. “In one set of experiments we let them see our impatient faces on computer screens.”
“Nothing in mental health will become clear unless we can look at the environment.”
This social stress activated two brain areas — but the pattern depended on the volunteers' histories of urban living. The amygdala, which processes emotion, showed much greater activity in people who were currently living in a city. And the cingulate cortex, which helps to regulate the amygdala and processes negative emotion, responded more strongly in those brought up in large cities than in those brought up in the countryside, irrespective of where they lived now. Meyer-Lindenberg thinks that this over-responsiveness to stress could make city-dwellers more prone to psychiatric conditions such as schizophrenia — and his results chime with the idea that stress in childhood or adolescence can have a lasting effect on the brain's development and increase susceptibility to psychiatric disease.
Other scientists are following Meyer-Lindenberg's lead. Daniel Weinberger, director of the Lieber Institute for Brain Development in Baltimore, Maryland (and a self-confessed addict “to the cultural stimulation of the city”), is planning a huge, long-term project to study environmental and genetic risk factors for schizophrenia in China, where urbanization is happening at lightning speed. The proportion of people living in cities there has doubled in the past two decades, to more than half. Together with colleagues at Peking University in Beijing, Weinberger hopes to study thousands of people who moved to Beijing from the countryside before they were 12 years old, after they turned 18 and between the two ages. He will use brain imaging and genetic analyses to try to understand how urban upbringing and genes alter cognition and reasoning, functions that are often disrupted in schizophrenia.
Researchers suspect that the stress of city living leads to psychiatric disease mainly in people who are already at risk because of other environmental stresses or because they carry risk genes. One candidate gene, the details of which have not yet been published, has emerged from a large brain-imaging study being conducted by Meyer-Lindenberg in Iceland. He chose more than 500 people who had been identified by the Reykjavik-based company deCODE Genetics as carrying rare mutations that confer a high risk of schizophrenia, and subjected them to functional magnetic resonance imaging tests similar to the ones he used in his city study. “We've already found that people carrying that one particular gene variant activate the cingulate cortex when they process social stress, just like those who were brought up in cities,” he says. He expects to find many more gene candidates through the project, which will run for several more years.
Expand
Identifying which parts of a busy city life are the most stressful is another massive challenge (see 'Stress and the city'). The common urban experience of feeling different from your neighbours because of socioeconomic status or ethnicity could be one factor, Meyer-Lindenberg thinks. If so, immigrant groups, who often experience isolation, may be processing stress in a similar way to city-dwellers. He is now testing this hypothesis in the children of immigrants to Germany. (First-generation immigrants are not suitable because the stress of social isolation could be confounded by the stress of moving country.)
Jim van Os, a psychiatrist
ในปี 1965 หน่วยงานด้านสุขภาพในแคมเบอร์เวล ไตรมาสที่คึกคักของลอนดอนนั่น southward เริ่มต้นส้นสูงผิดปกติ พวกเขาเริ่มที่จะเก็บระเบียนกรณีสำหรับทุกคนในพื้นที่ที่ได้รับการวินิจฉัยโรคจิตเภท โรคซึมเศร้า โรค bipolar หรือเงื่อนไขทางจิตเวชอื่น ๆ ทศวรรษต่อมา เมื่อจิตแพทย์ดูกลับผ่านข้อมูล เห็นแนวโน้มที่น่าแปลกใจ: อุบัติการณ์ของโรคจิตเภทมีน้อยสองเท่า จากประมาณ 11 ต่อ 100000 คนต่อปีในปี 1965 ถึง 23 ต่อ 100000 ในปี 1997 — ระยะเวลาเมื่อมีไม่มีเพิ่มขึ้นเช่นในประชากรทั่วไป (J. al. Boydell et Br. J. จิตเวช 182, 45-49; 2003) ผลยกคำถามในจิตใจของนักวิจัยจำนวนมาก: สามารถความเครียดของชีวิตในเมืองจะเพิ่มความเสี่ยงของโรคจิตเภทและโรคจิตสุขภาพอื่น ๆ หรือไม่nature.com/stressคำถามหนึ่งเร่งด่วนได้ ในปี 1950 น้อยกว่าหนึ่งในสามของประชากรโลกอาศัยอยู่ในเมือง กว่าครึ่งงามตามโอกาสของงานและโอกาส ทำทันที โรคจิตประกอบด้วยภาระโรคที่ใหญ่ที่สุดในโลกแล้วหลังจากติดเชื้อโรค และ แม้ว่าสถิติโลกยังแสดงมีการเพิ่มหลักในอุบัติการณ์ ต้นทุนสูงขึ้น ในเยอรมนี จำนวนวันลาป่วยที่ใช้สำหรับโรคจิตเวชสองเท่าระหว่าง 2000 และ 2010 ในอเมริกาเหนือ ค่า 40% ของความพิการ เรียกร้องสำหรับการขาดงานทำงานเกี่ยวข้องกับภาวะซึมเศร้า ตามประมาณการบาง "ดูเหมือนว่า เมืองอาจจะทำให้เราป่วย กล่าวว่า Boydell เจนที่สถาบันจิตเวชในลอนดอน ผู้นำการศึกษาแคมเบอร์เวลAnecdotally เชื่อมโยงระหว่างเมือง ความเครียด และสุขภาพจิตทำให้รู้สึก จิตแพทย์รู้ว่า ความเครียดสามารถทำให้เกิดโรคจิต — และชีวิตในเมืองที่ทันสมัยอย่างกว้างขวางถือว่าเป็นเครียด ประชาชนทั่วหน้าเสียงเพิ่มเติม อาชญากรรมเพิ่มมากขึ้น slums เพิ่มเติม และปรับบนท้องถนนมากกว่าที่ทำอยู่นอกพื้นที่เมืองคน ผู้ที่มีงานบ่นของการเติบโตความต้องการของพวกเขาในทำงาน ที่พวกเขาคาดว่าจะทำมากในเวลาที่น้อยกว่าแต่ความคิดไม่ได้กันทดสอบ ยากที่จะศึกษาว่าสิ่งซับซ้อนเป็น 'เมืองระบบ' มีผลกระทบกับสมองได้ การ complicate เรื่อง เมืองเติบโตมากรวมประชากรอพยพ ซึ่งมีความเสี่ยงของโรคทางจิตเวชที่เกี่ยวข้องกับการแยกทางสังคมอลิสันแอ็บพูดเกี่ยวกับความเครียดและใช้ชีวิตในเมือง00:00ไปเต็มพอดคาสต์ตอนนี้ นักวิทยาศาสตร์ไม่มีแก้ปัญหาหัวคำถามบน ใช้สมองทำงานภาพและการตรวจสอบดิจิตอลเพื่อดูว่าคนที่อาศัยอยู่ในเมืองและชนบทแตกต่างกันแบบว่า สมองพวกเขาประมวลผลสถานการณ์เครียด "ใช่ เมืองเครียดมีแนวคิดใหญ่ ยุ่ง แต่ฉันเชื่อว่า ควรจะไปดูถ้าสมองของประชาชนมองอย่างใดแตกต่างกัน น้อย" กล่าวว่า Andreas Meyer Lindenberg ผู้อำนวยการ สถาบันกลางสุขภาพจิตในมันน์ไฮม์ ประเทศเยอรมนี และถ้านักวิทยาศาสตร์ได้ว่าด้านใดของเมืองจะเครียดมากที่สุด ผลการวิจัยอาจช่วยได้เพื่อปรับปรุงการออกแบบของพื้นที่เขตเมือง "ทุกคนต้องการเมืองเพื่อความสวยงาม แต่ไม่มีใครรู้อะไรว่า, " Meyer Lindenberg กล่าวว่า ถนนกว้าง อาคารสูง ต้นไม้เพิ่มเติม "สถาปนิกตั้งทฤษฎีมาก แต่โครงการชนิดนี้สามารถส่งข้อมูลพื้นฐานทางวิทยาศาสตร์สำหรับรหัสเมือง"ความเครียด relentlessพิจารณาจากการมองวิวัฒนาการ ตอบสรีรวิทยาความเครียดเป็นสิ่งดี: จะช่วยเลี้ยงลูกด้วยนมจะอยู่รอด ภัยคุกคามใด ๆ ไม่ว่าจาก predator, dwindling เสบียง หรือ ศัตรูก้าวร้าว เรียกของฮอร์โมน cortisol และตื่นเต้น ฮอร์โมนเหล่านี้เพิ่มระดับน้ำตาลในเลือด และกระจายการไหลเวียนของเลือด ปอดและกล้ามเนื้อเพื่อให้สัตว์สามารถตอบสนองต่อการคุกคาม โดยการทำงาน การล่าสัตว์ หรือต่อสู้"โครงการชนิดนี้สามารถส่งข้อมูลพื้นฐานทางวิทยาศาสตร์สำหรับรหัสเมือง"Problems arise when the stress response doesn't switch off. Stress-hormone levels that stay too high for too long cause high blood pressure and suppress the immune system. And, although the mechanisms are unknown, scientists agree that severe or prolonged stress also raise the risk of psychiatric disease — most brutally in those who have a genetic predisposition, and when the stress occurs while the brain is still developing. In theory, then, the ceaseless challenges of the city could produce this kind of damaging stress. Some fear that they could end up driving an increase in mental illness around the world.The only signs of an increase, however, come from relatively small, local studies. “It's frustrating — we feel it should be rising,” says Ronald Kessler, a mental-health epidemiologist at Harvard Medical School in Boston, Massachusetts. “But globally we have not seen this, and there are also studies which indicate it isn't even rising in cities.” However, reliable data on the prevalence of psychiatric disease are hard to find because diagnoses are often imprecise or incompletely recorded. The Camberwell study was influential because, unusually, it captured all those who were diagnosed with a mental disorder, even if they were not admitted to hospitals, and the researchers involved carefully reviewed every case.Published in 2003, the Camberwell study deeply impressed Meyer-Lindenberg, who was then at the US National Institute for Mental Health in Bethesda, Maryland, researching how genetic risk factors for schizophrenia affect brain function. As a student in Manhattan some years earlier, Meyer-Lindenberg says, “I had been struck by the number of homeless mentally ill people on the streets, and the problems of the city somehow resonated with me”. He wondered if city living was somehow making the brain more susceptible to mental-health conditions. When he returned to his native Germany in 2007, he decided to tackle the question directly. But at the time, Meyer-Lindenberg says, “people said the effect would be too subtle to make sense of”.Yet the results of his study, published last year in Nature (F. Lederbogen et al. Nature 474, 498–501; 2011), clearly showed that people who grow up in cities process negative emotions such as stress differently from those who move to the city as adults. His team scanned the brains of 55 healthy volunteers as they carried out arithmetic tasks under a constant bombardment of negative social feedback. “We'd always let them know through headphones that we thought they were failing, or at least not doing as well as other subjects we'd had in the scanner,” says Meyer-Lindenberg. “In one set of experiments we let them see our impatient faces on computer screens.”“Nothing in mental health will become clear unless we can look at the environment.”This social stress activated two brain areas — but the pattern depended on the volunteers' histories of urban living. The amygdala, which processes emotion, showed much greater activity in people who were currently living in a city. And the cingulate cortex, which helps to regulate the amygdala and processes negative emotion, responded more strongly in those brought up in large cities than in those brought up in the countryside, irrespective of where they lived now. Meyer-Lindenberg thinks that this over-responsiveness to stress could make city-dwellers more prone to psychiatric conditions such as schizophrenia — and his results chime with the idea that stress in childhood or adolescence can have a lasting effect on the brain's development and increase susceptibility to psychiatric disease.Other scientists are following Meyer-Lindenberg's lead. Daniel Weinberger, director of the Lieber Institute for Brain Development in Baltimore, Maryland (and a self-confessed addict “to the cultural stimulation of the city”), is planning a huge, long-term project to study environmental and genetic risk factors for schizophrenia in China, where urbanization is happening at lightning speed. The proportion of people living in cities there has doubled in the past two decades, to more than half. Together with colleagues at Peking University in Beijing, Weinberger hopes to study thousands of people who moved to Beijing from the countryside before they were 12 years old, after they turned 18 and between the two ages. He will use brain imaging and genetic analyses to try to understand how urban upbringing and genes alter cognition and reasoning, functions that are often disrupted in schizophrenia.Researchers suspect that the stress of city living leads to psychiatric disease mainly in people who are already at risk because of other environmental stresses or because they carry risk genes. One candidate gene, the details of which have not yet been published, has emerged from a large brain-imaging study being conducted by Meyer-Lindenberg in Iceland. He chose more than 500 people who had been identified by the Reykjavik-based company deCODE Genetics as carrying rare mutations that confer a high risk of schizophrenia, and subjected them to functional magnetic resonance imaging tests similar to the ones he used in his city study. “We've already found that people carrying that one particular gene variant activate the cingulate cortex when they process social stress, just like those who were brought up in cities,” he says. He expects to find many more gene candidates through the project, which will run for several more years.ExpandIdentifying which parts of a busy city life are the most stressful is another massive challenge (see 'Stress and the city'). The common urban experience of feeling different from your neighbours because of socioeconomic status or ethnicity could be one factor, Meyer-Lindenberg thinks. If so, immigrant groups, who often experience isolation, may be processing stress in a similar way to city-dwellers. He is now testing this hypothesis in the children of immigrants to Germany. (First-generation immigrants are not suitable because the stress of social isolation could be confounded by the stress of moving country.)Jim van Os, a psychiatrist
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