October 5, 2022

Children in Norway born to immigrant mothers have 7 times the autism rate — but scientists aren’t sure why

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For some time, figures from the Norwegian healthcare system suggested that young children from a minority background seem to have above average risk of autism. This prompted researchers at St. Olavs Hospital in Trondheim to investigate this further — and their findings are quite concerning.

According to the finding of the study involving 142 children aged 2 to 6 diagnosed with autism spectrum disorder (ASD) from Sør-Trøndelag, a county in central Norway, children born to immigrant mothers were up to seven times more likely to develop autism symptoms than their peers born to Norwegian-born mothers. Furthermore, the children of foreign-born mothers — who became pregnant and delivered their babies within the borders of the Scandinavian country — also had a higher than average risk of developing more severe ASD symptoms.

Researchers are not sure what can explain these trends, but the findings suggest that the mothers’ immigrant backgrounds could impact the cognitive development of their children somehow — how exactly remains to be seen.

Immigration could be a more important risk factor for autism than previously believed

ASD is a collective term for diagnoses such as autism (childhood autism), Asperger’s syndrome, atypical autism, and other autistic traits. The classic signs of autistic behavior include communication difficulties, poor social skills, repetitive behavior, and narrowly focused interests.

In Norway, like in many other parts of the world, the rate of children diagnosed with ASD has risen tremendously over the years. This is mainly due to the fact that the definition of ASD has been expanded to include people that have difficulties with social interaction across a range of intellectual abilities. Decades ago, the diagnosis was only applied in the most apparent cases.

Compared to other countries, Norway has a very robust program for infant health care, which monitors the development of young children up to five years old regardless of their socioeconomic or ethnic background. So, for instance, if a child has difficulty speaking at ages 2-4, the case can be flagged for subsequent screening for ASD.

“This is a strength of our study, compared to similar studies in other countries. Finances and parents’ resources are not what determines whether your child will be referred to an examination,” Anne Lise Høyland, chief physician at St. Olavs Hospital and co-author of the new study, told Science Norway.

The study analyzed anonymized patient records for 142 children diagnosed with ASD between 2016 and 2019 in Sør-Trøndelag, which likely represent most if not all autistic children who were given a formal diagnosis during these years.

Researchers found that 0.74% of children in Sør-Trøndelag whose parents immigrated to Norway were diagnosed with ASD, compared to just 0.1% of children whose mothers had a Norwegian background. The children whose mothers had a foreign background also scored higher on an autism diagnosis test, averaging a score of 19 compared to 15.3 for children with ASD born to Norwegian mothers.

The seven to one ratio is puzzling, to say the least. It suggests an overdiagnosis of ASD children born to immigrant mothers, and an underdiagnosis of ASD children with Norwegian mothers, or quite possibly both. But the authors of the study point out that the deviations from neurotypical behavior are quite obvious, and the heightened risk of autism for children born to immigrant mothers can also explain why their symptoms are more severe.

A 2009 meta-analysis of 40 different international studies identified nearly 30 prenatal factors that may influence the risk of childhood autism, including being the oldest child, having a mother with gestational diabetes, or being exposed to medications, particularly psychiatric drugs, in utero. But also on the list was having a mother who was born abroad.

Another study reviewed patient data on nearly 5,000 children with ASD in Sweden. One in five had both parents born outside Sweden, most of whom hailed from Africa, western Asia, and northern Europe. Higher rates of autism with intellectual disability were found to be among children of parents who had come to Sweden from resource-poor countries. For instance, compared to children with ASD with two Swedish-born parents, the rate of autism with intellectual disability was twice as high among children whose parents were born in sub-Saharan Africa.

ASD is a complex condition likely owed to a confluence of factors working together, including genetics. But these recent findings suggest immigration could play a more important role in increasing the risk of autism than previously thought.

Why exactly immigration may be heightening the risk of ASD is not at all clear at this point, which is why further studies are warranted. Perhaps the stress of immigration on mothers could have immunologic consequences that later impact the development of children. Another possible explanation is the lack of vitamin D, specifically among African mothers who emigrated to northern latitudes.

To this day, most research on autism focuses on mostly white and middle-class families. Since it’s critical that kids with ASD get diagnosed early and gain access to high-quality treatment, an immigrant background could be more closely watched in the future, as far as autism diagnosis goes.

The new findings appeared in Tidsskriftet, the journal of the Norwegian Medical Association.

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