Meta-analytic reviews suggest that international migrants have a two to threefold increased risk of psychosis compared with the host population, and the level of risk varies by country of origin and host country. This increased risk may persist into the second and third generations. Incidence rates are not typically found to be elevated in the country of origin; therefore it is believed that the migratory or postmigration experience may play a role in the etiology.

The migration-related emergence of psychotics disorders is a potential concern in Canada, which receives 250,000 new immigrates and refugees each year. However, there is a notable lack of current epidemiological information on the incidence of psychosis among these groups.

So begins a new paper that seeks to answer a basic question: are there certain migrant groups more at risk of psychotic disorders in Canada?

This week’s Reading: “Incidence of psychotic disorders among first-generation immigrants and refugees in Ontario” by Kelly K. Anderson et al., which was published in the CMAJ in June.

Kelly K. Anderson

Of course, studying the incidence of psychotic disorders in immigrant populations isn’t exactly novel – there is a rich literature in this field. And the Canadian angle isn’t novel either – as the paper points out, previous studies have considered B.C. hospital admission rates for schizophrenia in European migrants in the early 1900s.

But this paper aims to consider recent data and Canadian data – relevant in a country that takes in 250,000 migrants a year. The paper focuses on Ontario, where first generation migrants constitute almost a third of the population.

Here’s what they did:

· Essentially, they used a retrospective cohort design to estimate the incidence of schizophrenia and schizoaffective disorders among immigrants and refugees in Ontario.

· Using Institute for Clinical Evaluative Sciences (ICES) data, patient records were linked with multiple Ontario health administrative databases. These data include physician and hospital services funded by OHIP. The study authors also linked data from Citizenship and Immigration Canada (CIC) that includes information on immigrants and refugees.

· Considering a ten-year window, they focused on schizophrenia and schizoaffective disorder. One of the following needed to be met for that classification: a discharge diagnosis of schizophrenia or schizoaffective disorder from a hospital bed; an Axis I diagnosis of either of those disorders from a psychiatric bed, 2 OHIP billing claims or ED visits with those diagnoses in a 12 month period.

· This algorithm was validated using administrative coding and ICES data.

· Analyzing the CIC-ICES data, researchers followed the cohort of Ontario residents retrospectively from 1999 for a decade, for people between 14 and 40 years of age.

Here’s what they found:

· The cohort included 4,284,694 people. 9.8% were first-generation migrants, with 22.7% having refugee status.

· “The degree and direction of risk varied by refugee status and the country of birth.” (See the table below.)

· “Immigrants from the Caribbean and Bermuda had a higher risk of having a psychotic disorder compared with the general population (IRR 1.60, 95% CI 1.29–1.98).”

· “Immigrants from northern Europe (IRR 0.50, 95% CI 0.28– 0.91), southern Europe (IRR 0.60, 95% CI 0.41– 0.90) and East Asia (IRR 0.56, 95% CI 0.41–0.78) had lower risks.”

· “Refugee status was an independent predictor of an increased risk of a psychotic disorder (IRR 1.27, 95% CI 1.04–1.56) among all migrants…”

Our findings suggest that particular immigrant and refugee groups may have a higher risk of psychotic disorders. Migrant status, in particular refugee status, needs to be considered as an important risk factor for psychotic disorders in Ontario.

The paper goes on to interpret these findings, highlighting three points:

Role of refugee status

As is consistent with the literature, the study found higher risk of psychotic disorders in refugees than non-refugees and the general population. The study authors wonder about adversity, trauma, and other characteristics seen more in refugees than in immigrants as a possible cause. They also note the challenges faced by refugees in Canada (as opposed to immigrants) as another possible explanation.

Role of visible minority status

As is also consistent with the literature, the study found higher rates of schizophrenia among certain groups: immigrants from Caribbean and Bermuda, refugees from East Africa and South Asia. The authors wonder if discrimination is a factor, and note an existing literature on discrimination and psychosis. But life isn’t so simple: they also note that some groups that may be discriminated against tended not to have higher rates of schizophrenia. (Take a look at the IRRs of immigrants from East Africa – high – versus the other parts of Africa – not high.)

Role of socioeconomic position

The paper notes the lack of literature on migrant groups that may be “protected compared with the host population.” Here they note that northern and southern European immigrants and those from East Asia all had lower rates of psychotic disorders. The study authors wonder about these groups being more established and better positioned socioeconomically. Interestingly, they speculate that Canada’s immigration policies – favouring English or French and the educated – may be protective in and of itself.

The paper concludes:

Given that Canada is currently experiencing a rapid growth in the population of foreign-born citizens — one of the highest rates of any Western nation — the mental health status of immigrants and refugees should be a national priority.

A few thoughts:

1. This is a good study.

2. I liked the Canadian focus of the study. They picked a well-researched topic, and made it relevant here.

3. The authors wonder about studying migrant groups with lower risk of psychosis to better understand what is “protecting” them. Fair point.

4. I also wonder about future work that considers public policy interventions. Are there specific Canadian programs (like housing programs, substance counseling or psychological interventions) that could be shown to be more useful in at risk groups? Are there programs that are not shown to be particularly useful?

5. Moving forward, as Canada continues to take in so many immigrants and refugees, the study authors final point is important. Immigration policy must include mental health policy.

Reading of the Week. Every week I pick a reading — often an article or a paper — from the world of Psychiatry.