Urban Living Increases Psychosis Risk in Only High-Income Countries

Bruce Link, distinguished professor of public policy and sociology, and member of the Center for Healthy Communities in the School of Medicine.

Urban residence, or urbanicity, is a well-established risk factor for psychotic disorder, but the evidence comes from primarily high-income countries in Europe and North America, as well as Australia.

A team of researchers, including UC Riverside’s Bruce G. Link, now reports in JAMA Psychiatry that urban living is not associated with psychotic experiences or psychotic disorders in other countries.

The team used data from the World Health Survey that includes information from more than 215,000 residents in 42 low- and middle-income countries, home to more than 80 percent of the world’s population.

“We found no association between urban residence and psychosis in these data, the largest and most internationally representative sample of low- and middle-income countries in which this topic has been studied,” said Link, a distinguished professor of public policy and sociology, and member of the Center for Healthy Communities in the School of Medicine. “The finding tells us that the risk of urban living is only present in high-income countries and therefore directs us to facets of urban living that may especially characterize urban life in-high income countries such as cannabis use, racial discrimination, and income inequality.”

Study participants were asked four “yes” or “no” questions about psychotic symptoms, including whether they had ever received a diagnosis of schizophrenia or psychotic disorder.

“Our findings point to urban living not being a risk factor for psychosis for the world’s population that lives in low- and middle-income countries,” said Jordan E. DeVylder, an associate professor in the Graduate School of Social Service at New York’s Fordham University and the paper’s lead author. “The association between urbanicity and psychosis may very well be a feature of industrialized countries only.”

Here are some highlights of their findings:

-Affluent members of society tend to populate suburban areas in high-income countries, which is not reflected in developing countries.

-Compared with low- and middle-income countries, high-income countries typically have relatively large immigrant and ethnic minority populations that typically reside in urban areas.

-Low- and middle-income countries are known to host most of the world’s refugees, particularly in urban areas, who may be at greater risk for psychosis.

-In high-income countries, cannabis use is more common in cities compared to rural areas, but it is less prevalent overall in most low- and middle-income countries.

Link and DeVylder were joined in the research by colleagues at the Royal College of Surgeons in Dublin, Ireland; USC; Universitat de Barcelona, Spain; and Centro de Investigación Biomédica en Red de Salud Mental in Madrid.

Iqbal Pittalwala


Researchers Shed Light on How and When Continents Emerged above Sea Level

Andrey Bekker, associate professor in the Department of Earth Sciences.

From space, Earth is like a blue and green marble — an almost equal mix of land and sea. But it wasn’t always that way. When Earth first formed, there wasn’t much continental crust standing above sea level, except for a few small islands floating in a global ocean called a water world. Exactly when and how continents emerged above sea level remains a contested topic in geology.

Now, a team of researchers, including one from UC Riverside, have expanded what we know about the time when Earth’s first large landmasses surfaced. The University of Oregon-led team studied isotopic clues left in ancient shales to pinpoint when the first continents emerged. Their findings suggest an abrupt surfacing of land above the ocean at about 2.4 billion years ago — possibly triggering dramatic changes in climate, atmosphere and ocean oxidation state, and life. The trigger for these dramatic changes about 2.4 billion years ago has puzzled scientists for several decades, and the paradigm is now shifting to cooling of the Earth’s mantle — the layer between the crust and the outer core — resulting in its higher viscosity to support larger landmasses and mountains above sea level.

The study was published May 23 in the journal Nature. UCR’s Andrey Bekker, an associate professor in the Department of Earth Sciences, provided most of the samples used in the study and the accompanying geological information, and also helped with data interpretation.

The work was supported by the National Science Foundation and National Sciences and Engineering Research Council. Read the paper here: https://www.nature.com/articles/s41586-018-0131-1

-Sarah Nightingale

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