Immigration policy played a decisive role in the outcomes of three regional elections in Germany this past Sunday. Chancellor Angela Merkel’s party in particular, the Christian Democratic Union, suffered losses attributed to its leader’s welcoming stance toward refugees fleeing war in Syria, Iraq and other war-torn regions. Germany took in more than a million migrants and refugees in 2015—more than any other country in Europe. But taking each nation’s population into consideration, Germany actually lags behind several other countries in the European Union, notably Hungary and Sweden, which have received proportionally larger numbers of asylum applications.

Although it is well established that compared with voluntary migrants, refugees face an increased risk of mental health problems such as depression, anxiety and post-traumatic stress disorder, very little is known about their risk for psychotic disorders such as schizophrenia. And although the causes of schizophrenia remain unknown, a large body of research has found that traumatic events can further increase the risk of or even trigger schizophrenia in individuals who may already be vulnerable.

In a new study published this week in BMJ (the British Medical Journal), a team of researchers in Sweden reported that refugees in that country were on average 66 percent more likely to develop a nonaffective psychotic disorder (psychoses unaffiliated with mood disorders) than nonrefugee migrants from the same regions of origin. Although it came as no surprise that they were also up to 3.6 times more likely to do so than the Swedish-born population—previous research has already found a greater risk of psychosis in migrants compared with the general population—this study went a step further by using data that distinguished between refugees and other migrants.

Source: “Refugee migration and risk of schizophrenia and other non-affective psychoses: cohort study of 1.3 million people in Sweden.” Hollander, et al. in BMJ, Vol. 352, 2016.

Graphic by Amanda Montañez

The researchers, based at the Karolinska Institute and University College London (U.C.L.), used national anonymized databases to identify population and health information for more than 1.3 million people born after 1984 (excluding people younger than 14 years old). The data included individuals who were born in Sweden to Swedish-born parents as well as migrants and refugees from the Middle East, north Africa, sub-Saharan Africa, Asia, eastern Europe and Russia. The research team kept track of all new cases of nonaffective psychotic disorders diagnosed until 2011 and compared incidence rates across the three different populations, adjusting for age, sex, disposable income and population density.

The findings provide a first step toward better understanding risk factors for nonaffective psychosis, according to Anna-Clara Hollander, a psychologist at Karolinska and the study’s lead author. “By distinguishing between refugees and nonrefugee migrants, this study shows that although being a refugee doesn’t explain it all, traumatic experiences or stress is part of the etiology of nonaffective psychosis,” she says.

If that’s the case, however, then the source of that trauma and stress remains an open question. The Swedish registry data used in this study provided no information as to whether refugees’ increased risk stemmed from their experiences before, during or after migration. “I’m nervous that these findings will be taken out of context,” says Mina Fazel, a psychiatrist at the University of Oxford who did not take part in the study. “We need to understand more. This study is interesting and important in highlighting the increased vulnerability of the refugee population. But that doesn’t necessarily mean that the refugee experience caused that. It’s not clear what’s causing this increased rate of nonaffective psychosis.”

Robin Murray, a psychiatrist at King’s College London who is also not affiliated with the study, agrees, emphasizing that although trauma has been shown to increase the risk of psychosis, so have discrimination and racism. “Is it because these refugees are coming from somewhere where they’ve seen their families butchered and suffered some kind of trauma?” he asks. “Or is it because as refugees they had to wander across half of Africa for a couple years before they ever got to Europe? Or is it because that when they got to Europe and eventually Sweden, they lived in fear of being kicked out of the country?”

Where you are from matters

In fact, how the study’s findings are interpreted rely very much on the answers to these questions. The researchers found that increased rates of nonaffective psychotic disorders in refugees compared with nonrefugees were significant for all regions people hailed from except sub-Saharan Africa. For this area, incidence rates of psychosis in all migrants were similarly elevated compared with people born in Sweden. James Kirkbride, a psychiatric epidemiologist at U.C.L. and one of the study’s authors, turns his attention to premigration experiences, attributing the finding to the possibility that both refugees and nonrefugee migrants leaving sub-Saharan Africa for Sweden may have been exposed to similar types of trauma. “It’s possible that for people from this region, refugee status matters a little less,” he says. “Other migrants may have been exposed to other adversities: famine, war…. Some may have become refugees but they would have all been exposed to the same underlying risk factors of schizophrenia. Whereas perhaps in eastern Europe, where those events happen to a lesser extent, there’s a clearer distinction between those who are refugees and those who are nonrefugee migrants.”

Murray is more skeptical of this line of reasoning. “Another explanation is that sub-Saharan migrants coming to Sweden feel more alienated or find it more difficult to integrate into society,” he says. “One could be politically incorrect and say right-wing politicians who are hostile to migrants probably make them feel even less welcome in society and more prone to psychiatric illness. You have a very good example of this in the States now. If I were a Mexican migrant to the U.S. and already had a tendency toward paranoia, it would be amplified just by watching CNN.”

And in comparing refugee and nonrefugee migrant populations at all, Fazel explains, it’s important to keep in mind that different ranges of risks may be represented in each group, even if both are considered at-risk for psychosis. For instance, migrants from a given region may have the benefits of education, socioeconomic advantage or good health, which may not be the case for refugees from the same region. “These are really big groups, and people in those groups have vastly different experiences. For example, by looking at eastern Europe and Russia as one region, you’ve got data from a refugee fleeing the Balkans, and you’re comparing it to data from someone very prosperous from Russia who chooses to migrate to Sweden. So you have to be careful about the conclusions you draw from this,” Fazel says.

The researchers agree, however, that what’s needed now is a more concerted effort on the part of host countries to address these problems and provide better mental health screening for refugees. “With this paper, I fear putting a vulnerable group into a more stigmatized situation,” Hollander says. “On the other hand, addressing these issues is the only way to support those affected and find ways to prevent and rehabilitate.” She emphasizes the need for greater awareness on the part of clinicians and service planners in high-income settings.

“We’re at this point where in Europe, large populations of refugees are arriving, many from areas of conflict,” Fazel says. “It’s a unique opportunity to study the mental health factors that influence refugee populations—to explore the social factors at play, understand positive and negative influences, and then learn to alter our asylum policies with that kind of data in mind.” Those who provide services to refugees and immigrants, she adds, “need to understand some of the risk factors and be more in tune with trying to identify them and treat them.”