Background: Autism spectrum disorder (ASD) is an umbrella term covering a range of conditions characterised by challenges with social interaction, restricted interests and repetitive behaviours. The prevalence of ASD has increased significantly in recent years, and there is a clinical impression of a preponderance of cases among young children whose mothers were not born in Norway.
Material and method: The study included 142 children aged 2 to 6 years who were diagnosed with autism in the county of Sør-Trøndelag, Norway in the period 2016-2019. The following information was collected: age at onset of symptoms and diagnosis, primary diagnosis, ADOS-2 (Autism Diagnostic Observation Schedule) scores, whether the child was born in Norway and the mother's country of birth.
Results: Children of mothers born outside of Norway had a 7.7 times higher risk of being diagnosed with autism than children of Norwegian-born mothers, with an annual incidence of 0.74 % and 0.10 % respectively. These children were diagnosed earlier, at an average age (standard deviation) of 41.9 (11.8) and 51.8 (18.1) months respectively (95 % CI 4.7 to 15.2); a p-value of <0.001 for the difference. They also had a higher ADOS score, with an average (standard deviation) of 19.0 (6.2) and 15.3 (7.1) respectively.
Interpretation: The preponderance of autism diagnoses may be an indication that the mothers' country of origin has an impact on the development of the condition. This has implications for adaptions to the assessment and follow-up of this patient group.