A new study underlines the risk of developing psychoses and psychological disorders, such as schizophrenia, among refugees as their lives are marked with the trauma of fleeing persecution, wars and natural disasters.

The study of 1.3 million people in Sweden reveals that refugees are at three times higher risk of experiencing psychotic disorders, such as schizophrenia, as compared to the native-born residents.

 The research was published Tuesday in the journal BMJ.

"The dramatically increased risk among refugees shows that life events are a significant risk factor for schizophrenia and other psychoses," lead author Anna-Clara Hollander, of Sweden's Karolinska Institute, said in a release.

Refugees were also at two-thirds higher risk to develop such psychological disorders as compared to migrants, who migrated from the same regions for other reasons, such as economic factors.

Researchers in the Sweden study said that this was the first study to examine the risk of schizophrenia and other psychoses among refugees.

"Clinicians and service planners in high income settings should be aware of the early signs of psychosis in refugees," the authors wrote. "Just as for the general population, refugees and their families will benefit from timely and early intervention and care, particularly in those exposed to severe psychosocial adversity."

Refugees are already known to be at risk to developing post-traumatic stress disorder and depression. Previous studies have revealed that being an immigrant is a risk factor for schizophrenia. 

For the study, the data researchers analyzed data from Sweden's national registry, which tracks immigration and health status for individuals. The data included 1.3 million people who were born after 1983. The researchers followed them from their 14th birthday until the end of 2011.  The researchers found that of the total of this group, 3,704 experienced a psychotic disorder.

"These differences cannot be explained by other, important alternative explanations like differences in age, sex, income or urban residency," said co-senior author James Kirkbride of the University College London.

The refugees in the study included migrants from the Middle East and North Africa, sub-Saharan Africa, Asia and Eastern Europe, including Russia.

The study noted that refugees from sub-Saharan Africa had the greatest risk for experiencing schizophrenia.

Sweden grants more asylum applications per capita than any other high-income country. In 2015, Sweden took in 163,000 asylum seekers. However, in 2016, that number decreased drastically after Copenhagen introduced national border controls to control the refugee flow.

Cornelius Katona, medical director of the Helen Bamber Foundation in London, noted in an editorial the researchers' lack of information on racism, discrimination and other post-migration risk factors.

"Consideration also needs to be given to the challenges that asylum seekers face during what is often a prolonged and distressing process," Katona wrote. These factors may include institutional detention, inability to work (and resultant deskilling and loss of self esteem), destitution and difficulty in accessing health and social care."