Syndemic Effects May Explain Ethnic Disparities in Psychotic Experiences

Higher rates of nonaffective psychosis among British minority populations may be tied to syndemic effects, according to a study published in The British Journal of Psychiatry.

Originally conceptualized by medical anthropologist Merrill Singer, a syndemic can be defined as “an aggregation of two or more diseases or other health conditions in a population…that exacerbates the negative health effects of…the diseases.” In this study, Jeremy Coid, MD, emeritus professor of Forensic Psychiatry at Queen Mary University, London, United Kingdom, and colleagues sought to explain ethnic inequalities in psychotic experiences based on individual risk factors and place-based disadvantages.

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The researchers performed a cross-sectional survey of 3725 British men aged 18 to 34 years, oversampling from black and minority ethnic communities and focusing nationally and in Hackney. They evaluated 19 measures in 4 domains, including sexual health, substance dependence, psychiatric illness, and violence/criminality, and administered the Psychosis Screening Questionnaire. Psychiatric history, as well as depressive and anxiety symptoms, were assessed. Statistical analyses included logistic regression and confirmatory factor analysis.

Compared with white men from the general population, black and South Asian men were more likely to live in areas characterized by deprivation in multiple areas. Overall, black men on a national level more often reported psychotic experiences, although this result did not occur after adjusting for social position.

In the syndemic model developed by the investigators, there was evidence of positive interactions between high-risk sexual behavior and violence/criminality in the relationship with psychosis and anxiety.

Additionally, they noted a syndemic effect between substance dependence and sexual health on psychotic experiences and anxiety. Scores for general syndemic factor were not significantly different for black and white men in the national survey, but scores were significantly higher for all groups in Hackney than for white men nationally.

The study authors noted that social status and neighborhood effects attenuated ethnic disparities in psychotic experiences, a result that corresponds with findings in American studies. Overall, the study outlined a syndemic of psychotic experiences, anxiety, substance dependence, high-risk sexual behavior, and criminality/violence.

The researchers wrote, “we require a public mental health approach to prevention and control, not only of the syndemic components, but the forces that originally determined and now tie these components together.”


Coid J, Gonzalez-Rodriguez R, Kallis C, et al. Ethnic disparities in psychotic experiences explained by area-level syndemic effects [published online October 30, 2019]. Br J Psychiatry. doi:10.1192/bjp.2019.203