As Europe’s borders continue to bulge under the weight of displaced refugees desperately seeking a passage to safer ground, a new study has revealed that the psychological trauma suffered by many of those affected by the crisis could persist long after their journey ends. Examining schizophrenia rates in Sweden, researchers found that refugees granted asylum in the Scandinavian country were 3.6 times more likely to develop the condition than the Swedish-born population.

To conduct the study, the researchers collected data relating to more than 1.3 million individuals, including refugees, non-refugee migrants from the same geographical regions, and those who were born in Sweden. Information was obtained from several national databases such as the national patient register, which provides details of all officially recorded medical issues, and the immigration and emigration database, which contains data relating to the status of all migrants and refugees in Sweden.

All selected participants were born on or after January 1, 1984, and were retrospectively followed from their 14th birthday – or their date of arrival in Sweden, if older than 14 at the time – until December 31, 2011. Publishing their findings in BMJ, the study authors report that during this period, refugees were also 66 percent more likely to be diagnosed with schizophrenic or other non-affective psychotic disorders than non-refugee immigrants from the same countries.

Non-affective psychosis is an umbrella term covering all short-lived episodes of acute mental illness involving a disrupted sense of reality, as opposed to mood-related or emotional disorders. It can be caused by a number of genetic and environmental factors, and has been found to be prevalent among those suffering from post-traumatic stress disorder (PTSD).

PTSD is a condition whereby distressing memories spontaneously interrupt regular thoughts, and is likely to be common among people fleeing humanitarian crises. Among the refugees in the study were those who had been displaced by conflicts in Afghanistan and Iran, and famine in East Africa – many of whom would have experienced highly traumatic episodes.

Based on this evidence, the study authors suggest that those fleeing more recent crises in places such as Syria and Kosovo could well face an equally high risk of developing non-affective psychosis, and suggest that health officials pay attention to early signs of such disorders in refugee populations. On a broader level, the findings also add to the growing body of evidence that exposure to psychosocial adversity in general leads to an increased risk of schizophrenia and other forms of psychosis.