Prevalence of Psychotic Disorders Increased in Immigrant Populations

Immigrant populations tend to have nearly 2 times the prevalence of psychotic disorders compared to the general population of the host country.

Immigrants from the Caribbean, Bermuda, East Africa, and South Asia have between a 1.5 and 2 times higher risk for psychotic disorders compared to the general population, according to findings published in CMAJ.

Researchers from the Centre for Addiction and Mental Health in Toronto, Canada compared immigrants from the Caribbean, Bermuda, East Africa, and South Asia to the general population from the Ontario, Canada area in order to determine the risk for psychotic disorders in this population. The researchers noted that this is one of the largest studies of its kind to date.

Participants aged between 14 and 40 years were followed for 10 years beginning in 1999 to see whether the incidence of psychotic disorders — specifically schizophrenia and schizoaffective disorder – differed between particular groups of immigrants. The incidence rate of psychotic disorder was 55.6 per 100,000 person years among the general population, while for immigrants, it was 51.7 per 100,000 person years. Among refugees, the incidence rate of psychotic disorders was 72.8 per 100,000 person years.

“We found that refugees had about a 25 percent greater risk of psychotic disorders compared to immigrants,” lead author Kelly Anderson said in a press release. “We also found that neighborhood-level income acted as a protective factor, with migrants who were living in the wealthiest neighborhoods in the province having half the risk of psychotic disorders compared to migrants living in the poorest neighborhoods in the province.”

The researchers believe this adds to existing substantial evidence from various countries which indicated that immigrants are at a higher risk for developing psychotic disorders compared to the host countries’ populations. The risk, the investigators believe, carry into the second generation. One hypothesis states that there is something inherent to the immigration process or the post migratory experience that may factor into the cause of psychotic disorders among immigrant groups.

“The patterns we observe suggest that psychosocial factors associated with the migratory experience and integration into Canada may contribute to the risk of psychotic disorders,” Paul Kurdyak, senior author of the study, continued in the statement.

The researchers continued that some immigrant groups have lower rates of psychosis, and they will work to determine the cause. They eventually want to develop prevention strategies for all.