May 17, 2018
2 min read

Urbanicity may not increase risk for psychosis in lower income countries

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Jordan DeVylder, PhD
Jordan E. DeVylder

Contrary to established findings that urbanicity is a risk factor for psychotic disorders, newly published study results demonstrated that urban living may not be linked to a higher risk for psychosis in low- and middle-income countries.

“Most studies of urbanicity and psychosis have been conducted in high-income countries in Europe or North America or in Australia. The association between urbanicity and psychosis is understudied in low- and middle-income countries (LMICs), although LMICs are home to greater than 80% of the world’s population,” Jordan E. DeVylder, PhD, of the Graduate School of Social Service, Fordham University, and colleagues wrote. “Some factors that characterize urban-rural differences in high-income countries may not generalize to many LMICs, where urban living may indicate greater access to resources rather than greater exposure to social adversity.”

To examine whether urban living was associated with higher odds of psychosis in LMICs, researchers conducted an international population-based study using cross-sectional survey data collected as part of the WHO World Health Survey from mid-2002 through 2004. They measured participants’ psychotic experiences using the WHO Composite International Diagnostic Interview psychosis screen and assessed self-reported lifetime history of any psychotic disorder diagnosis. A nationally representative cohort of 215,682 adults living in urban and nonurban areas in 42 LMICs were included in the study.

Analysis revealed that urban residence was not linked to psychotic experiences (OR = 0.99; 95% CI, 0.89-1.11) or psychotic disorder (OR = 0.89; 95% CI, 0.76-1.06) among the participants living in LMICs. At the country-level, there was a significant positive relationship between urban residence and psychotic experiences in Laos, Mali, Estonia, Mexico and Morocco, and a significant negative link between urban residence and psychotic experiences in Nepal, Vietnam, Hungary and South Africa.

After performing pooled analyses and meta-analyses of within-country effects, researchers found that the overall risk for psychotic experiences (OR = 0.97; 95% CI, 0.87-1.07) and psychotic disorders (OR = 0.92; 95% CI, 0.73-1.16) were similar among participants living in LMICs. There was a moderate level of heterogeneity between countries (I2 = 61%; 95% CI, 45%-72%).

“These findings contrast with the existing body of literature on this subject, which has been conducted primarily in high-income countries,” DeVylder and colleagues wrote. “This divergence suggests that the association between urbanicity and psychosis, rather than being a universal phenomenon, may be a feature of industrialized countries only. Further research is needed to clarify the causative factors underlying this differential relationship between LMICs and high-income countries.”

Evidence that explains the urban-rural differences in schizophrenia are lacking, even though it has long been studied, Oleguer Plana-Ripoll, PhD, of the National Centre for Register-Based Research, Aarhus BSS, Denmark, and colleagues wrote in an invited commentary.

“If these findings are mediated by social adversity and neighborhood-level stressors, then the research community will need to revise and particularize hypotheses for some countries but not others,” Plana-Ripoll and colleagues wrote. “New hypotheses and targeted research investments are strongly needed in this field. This will be the challenge for the next generation of researchers.” – by Savannah Demko

Disclosures: The authors report no relevant financial disclosures. Plana-Ripoll reports support from the Danish National Research Foundation. Please see the full study for other commentary authors’ relevant financial disclosures.