Hannah E. Jongsma
Results from a 17-site, international incidence study confirm marked heterogeneity in risk for psychotic disorders by person and place, such as higher rates in younger men, racial/ethnic minorities and areas characterized by a lower percentage of owner-occupied homes.
“The [WHO] Ten-Country Study, the most recent multicenter international study of the incidence of psychotic disorders, was widely interpreted as demonstrating worldwide homogeneity in rates of schizophrenia and other psychotic disorders,” Hannah E. Jongsma, MPH, from the department of psychiatry at the University of Cambridge, and colleagues wrote in JAMA Psychiatry. “To our knowledge, there has been no international comparison of the incidence of psychotic disorders since the [WHO] study.”
Prior research has shown that psychotic disorders differ significantly across social and environmental factors, including higher rates among men, younger adults, racial/ethnic minorities and with urban birth and upbringing.
Researchers sought to determine the incidence of psychotic disorders using similar methods across 17 international catchment areas in 6 countries and the differences between catchment areas by environmental risk factors. From May 2012 to April 2015, researchers examined 2,774 individuals from England, France, Italy, the Netherlands, Spain and Brazil who experienced a first episode of nonorganic psychotic disorders identified during 12.9 million person-years at risk. Confounders included age, sex and racial/ethnic minorities. Catchment area-level exposures included latitude, population density, percentage unemployment, owner-occupied housing and single-person households.
Overall, 2,183 patients (78.7%) had nonaffective psychotic disorders. After accounting for age, sex and racial/ethnic minority status, the researchers observed an eightfold variation in the incidence of all psychotic disorders, from six (95% CI, 3.5-8.6) per 100,000 person-years in Santiago, Spain, to 46.1 (95% CI, 37.3-55) per 100,000 person-years in Paris. The incidence rates were higher among racial/ethnic minorities (incidence rate ration [IRR], 1.6; 95% CI, 1.5-1.7), highest for men aged 18 to 24 years, and lower in areas with more owner-occupied houses (IRR, 0.8; 95% CI, 0.7-0.8). Jongsma and colleagues saw that these patterns were similar for nonaffective psychoses. Notably, a lower incidence of affective psychoses was linked to higher area-level unemployment (IRR, 0.3; 95% CI, 0.2-0.5).
“I think this study confirms something that clinicians have known for a long time: Someone's risk of developing a psychotic disorder varies by place and person,” Jongsma told Healio Psychiatry. “This knowledge is probably most useful for policy makers and those who plan health services, as it sheds some light on where services might be most needed. I think for clinicians on a day-to-day basis, it is probably mostly a reminder to take someone's social environment into account in designing the best treatment plan.”
In a related editorial, Ezra Susser, MD, DrPH, from the department of epidemiology at Colombia University Mailman School of Public Health and New York State Psychiatric Institute, and Gonzalo Martínez-Alés, MD, MSc, from the Universidad Autónoma de Madrid and the department of psychiatry at La Paz University Hospital in Spain, wrote that these findings should spark serious debate and show the necessity of further study.
“This study shows how far this field has advanced and how far it has yet to go. Our understanding of how the effect of individual experiences interact with or reflect the broader social context at multiple levels is ever advancing but quite incomplete,” they wrote. “These results of the study by Jongsma [and colleages] underscore the need to continue to refine both theories and measurements of the relationships between sociocultural environmental factors and psychoses, to seize opportunities to examine interactions at multiple, strategically chosen levels via strong study designs, and to use new opportunities to extend these studies across the globe.” – by Savannah Demko
s: The authors report no relevant financial disclosures.