Risk of autism seven times higher in Norwegian children with immigrant mothers
A study was conducted after health professionals started noticing a concerning pattern.
Researchers concluded in a recent Norwegian study that children of foreign-born mothers have a far higher risk of being diagnosed with autism. The study included 142 children aged 2-6 years old with an autism diagnosis in Sør-Trøndelag in mid-Norway.
The risk of autism in these children was just over seven times higher if the children were born of immigrant mothers.
The over-representation of this population indicates that the mothers' immigrant backgrounds may impact the development of autism, the researchers behind the study write in an article in Tidsskriftet, the journal of the Norwegian Medical Association.
Health personnel impressions
Anne Lise Høyland is one of the authors behind the study. She is a researcher and chief physician at st Olavs Hospital in Trondheim.
“As someone who works with examining and diagnosing children with autism, I saw over time that more and more of these children had mothers born in other countries than Norway”, Høyland says to sciencenorway.no.
Her colleagues at other regional hospitals noted the same development.
The impression was also that the condition was more serious in these children.
Figures from the Norwegian Patient Registry (link in Norwegian) suggested an increased risk of autism in young children with a minority background as well.
“When so many were experiencing this as a trend – we needed numbers to confirm whether it was actually true,” Høyland says.
So she recruited a medical student to collect the data and do the study. Together with two other colleagues from St. Olav's hospital and NTNU they wrote up the recently published article.
The researchers have reviewed the anonymised patient records of all the 142 children who were diagnosed with an autism spectrum disorder at various health institutions in Sør-Trøndelag in the years 2016 to 2019. Høyland believes the study includes all the children in this area who were given the diagnosis during these years.
Norway has an infant health care programme for children aged 0-5 years old. Development that deviates from the norm will easily be picked up in this transparent system, according to Høyland.
“Norway is well regulated in this regard. This is a strength of our study, compared to similar studies in other countries. Finances and parent’s resources is not what determines whether your child will be referred to an examination”, she says.
- Because autism includes a number of subgroups of diagnoses – like childhood autism, Asperger's syndrome and several others – and because it can be difficult to distinguish these from each other, professionals today often use the term autism spectrum disorder.
- Autism is still a term that can be used, as long as we are aware that this designation can refer to several different diagnoses that vary greatly in how serious they are. Professionals therefore talk about a range of disorders now.
- Autism is also no longer considered a rare condition. The incidence of autism spectrum disorders has increased sharply worldwide over the past 25 years and is now estimated to affect one to two percent of the population. Boys are diagnosed with autism three to four times more often than girls, but girls are at greater risk of not being diagnosed.
Sources: NHI, SNL, regjeringen.no
More severe autism
Four different autism diagnoses were included in the study.
The researchers found that 0.74 percent of all children with a country background other than Norway were diagnosed with autism. Only 0.10 per cent of children who had a mother with a Norwegian background received a similar diagnosis.
Children of mothers with a foreign country background also had higher average scores on the autism diagnosis tool used, averaging a score of 19.0 while children of Norwegian-born mothers averaged a score of 15.3.
This means the children with foreign born mothers had more severe autism.
The younger the child – the higher the autism score was, regardless of country background. This likely indicates that the developmental problems in these children are caught early and examined, as the symptoms are more serious.
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Not due to cultural differences
The authors write that scores on autism diagnostic tools may differ if the doctor and the children examined do not speak the same language or share the same cultural background.
Høyland does not believe that this is what causes the difference in the severity score in children in their study.
“These children have a development that is so deviant from normal development that they are noticed in the system. These are children aged perhaps 2-4 years old who do not speak”, she says.
The children will normally be exposed to the Norwegian language in kindergarten, and perhaps a different language at home. Parents however take part in the examination.
“My experience is that there are clear differences here. And perhaps that which gives a higher risk of autism also is the reason for why the autism is more severe”, she says.
Several European studies have previously found similar results. These studies found that especially children of mothers who immigrated from low-income countries may have more severe autism.
"Our findings underline the need for further studies of the significance of maternal immigration for the development of autism spectrum disorders," the researchers write.
They also point out that it is important to facilitate the assessment and follow-up of autism for people with a mother tongue other than Norwegian and a different cultural background.
These services should include customized diagnostics, interpreting services and available information in the mother’s mother tongue.
Should lead to more studies
The mothers in the study have various country backgrounds – from Norway’s neighbour Sweden to different Asian and African countries.
Their children were mostly born in Norway, and the mothers were pregnant in Norway.
“So this is not a result of being born or being pregnant during war or while fleeing”, says Høyland.
She emphasizes that the study was done in order to confirm an impression – which it did. As such, it raises more questions than it can answer.
“Is it migration, can it be due to genetic factors in the countries the mothers come from – they come from very different countries. What does it mean to migrate, does it have immunologic consequences? This gives us an impetus to study a lot of factors more closely”, she says.
The researchers just received funding to do the same study for children aged 12-16. Høyland does not have the impression that the same will be true for this group.
What she would really like to do, is follow up on the 142 children in the recently published study and see how they’re doing ten years later.
This is autism
- People with autism have deficient or deviant abilities for contact and social interaction with other people.
- Some people with autism may have normal or even higher abilities than others in some areas.
- Autism often occurs before children are three years old.
- The child's behaviour can be compulsive, monotonous and repetitive.
- Language development may be delayed.
- Autism can present challenges in kindergarten, school and working life.
- Many individuals with autism and Tourette's also have other diagnoses, such as ADHD, anxiety disorders and obsessive-compulsive disorder. About 30 percent of people with an autism diagnosis also have a developmental disability diagnosis.
Sources: Tidsskriftet, NHI, SN and regjeringen.no
A small study
Kristin Andersen Bakke comments on the new study from Sør-Trøndelag in her editorial in Tidsskriftet. Bakke is a specialist in paediatrics at Oslo University Hospital.
Bakke believes that it is difficult to explain biologically why parents with an immigration background seem to be a risk factor for autism.
She notes that the study by the four Trøndelag researchers is relatively small. At the same time, it points in the same direction as other international studies.
Training and facilitation
Bakke also considers it important to remember that people with autism are a very heterogeneous group. The condition presents very differently from one person to the next.
Autism spectrum disorders range from people with Asperger's syndrome who may have both normal and high intelligence to people with severe developmental disabilities.
No medical treatment can directly affect the core symptoms of autism.
The most important support measures for individuals with autism are training and facilitation, Bakke writes.
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The big question is why
Terje Nærland is a psychologist and senior researcher at Oslo University Hospital who specializes in neurodevelopmental disorders such as autism. He was not involved in the study from Trondheim.
Nærland says the finding of an overrepresentation of severe autism among children with non-Norwegian mothers, seems robust. The numbers found in the Trondheim-study - a more than 7 times greater risk - are very high, he says. But such overrepresentation has been reported also in other counties in Norway.
"The big question of course is why," he says.
The fear of researchers who count and find results like this is that people start speculating about this "why", and find reasons in cultural differences, or parenting styles - which was a hot theory in the 1940s and 50s.
"My research takes as its starting point that autism is a biological phenomenon which mainly is the result of genetic differences", Nærland says.
Known risk factors and genetics
Counting and finding differences in the patterns of a disease in a population is a good starting point.
“But this research needs to be followed up with more thorough studies,” Nærland says.
“The main risk factor for autism is genetics, this should be investigated in these samples. Genetic analysis should be done both for the children and for their parents. We probably also need to combine such thorough genetic studies with information about environmental effects, which as we know by now, are mainly related to the immune system,” he says.
Before thorough research is done on the known risk factors, speculation about other causes of autism in these populations is not warranted, Nærland states.
Prevalence varies in different countries
The fact that the prevalence of a disease varies according to country background is in itself not odd, Nærland points out.
“Several diseases have very different occurrences in different parts of the world,” he says.
However, although the prevalence of autism varies in different countries, no country has a seven times higher occurrence than others, according to the researcher.
At the same time, it's mostly western countries that have solid studies establishing prevalence, while numbers for many non-western countries are less certain.
The researcher confirms Anne Lise Høyland's statement that the results are most likely not due to cultural differences between doctor and patient when using the autism diagnostics tools.
"Tools obviously work less well if we don't understand each other properly. But this does not explain the effect we see here. The children in this study are quite severely affected. We're not talking small nuances in social behaviour, but lack of language. Then it matters less how precise the tool is," he says.
Kristin Brobakken Eig, Maria Brandkvist, Stian Lydersen and Anne Lise Høyland: Autism spectrum disorders in preschool children in Sør-Trøndelag 2016–19, article in Tidsskriftet, 2022.
Kristin Andersen Bakke: Autism or autisms?, editorial in Tidsskriftet, 2022.
Read the Norwegian version of this article at forskning.no