medwireNews: Foreign-born adoptees have the highest rates of psychiatric disorders among migrants, show the results of a large, Danish population-based cohort study.
Compared with native Danes, individuals born to parents in foreign countries but adopted by Danish parents had a significantly increased risk for any psychiatric contact (incident rate ratio [IRR]=1.65) - psychiatric hospital admission or outpatient care.
Foreign-born adoptees were also more likely than native Danes to be diagnosed with schizophrenia (IRR=2.52), schizophrenia spectrum disorders (IRR=2.47), schizoaffective disorder (IRR=2.40), bipolar affective disorders (IRR=2.15), affective disorders (IRR=1.47), anxiety and somatoform disorder (IRR=1.47), personality disorders (IRR=2.07), and substance abuse disorders (IRR=1.55).
"Foreign-born adoptees had significantly increased IRRs for all outcomes," investigators Elizabeth Cantor-Graae (Lund University, Sweden) and Carsten Pedersen (University of Aarhus, Denmark) write in JAMA Psychiatry.
Furthermore, this group of migrants "had by far the highest IRRs for all outcomes compared with those in other migrant status categories." This included first- and second-generation immigrants, native Danes with a history of living in a foreign country as a child, and those born abroad to Danish expatriates.
The study involved 1,859,419 individuals born between January 1, 1971 and December 31, 2000 and who were residing in Denmark by their 10th birthday. Information on the development of psychiatric disorders was obtained from outpatient and inpatient data held in the Danish Psychiatric Central Research Register.
"To our knowledge this is the first study to consider the full spectrum of psychiatric outcomes in relation to a foreign migration background," the researchers note. Previous studies have reported that there is a high risk for schizophrenia and other psychotic disorders among first- and second-generation immigrants, but they have not considered other diagnoses or groups of individuals, the team explains.
The study also showed that first- and second-generation immigrants had a significantly increased risk for developing schizophrenia and schizophrenia spectrum disorders if both of their parents had been born abroad. Second-generation immigrants with one foreign-born parent had a significantly increased risk for all psychiatric disorders.
And, native Danes who had a history of living in a foreign country had increased IRRs for bipolar affective disorder, affective disorders, personality disorders, schizophrenia spectrum disorders, and schizoaffective disorder.
This suggests that "residence aboard, rather than having foreign-born parents or racial/ethnic minority status, may increase the risk for developing psychotic disorders," Cantor-Graae and Pedersen conclude.
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