Autism diagnoses in school-age children in southern Trøndelag 2016-2019.

Background: We have previously reported a significantly higher prevalence of autism spectrum disorders in southern Trøndelag among preschool children with mothers from a different national background than Norway. In this study, we wanted to investigate whether, in the same period and in the same geographic area, there was also an excess prevalence among school-age children. Additionally, we wanted to identify psychiatric and developmental comorbidities.

Material and method: We carried out a retrospective review of the medical records of children between 10 and 16 years of age who had been diagnosed with autism in the period 2016-19.

Results: Out of a sample of 125 children, 18 had mothers with a different national background. This gave an incidence rate of 0.18 %, against 0.12 % for children with mothers born in Norway (relative risk 1.5; 95 % confidence interval 0.87 to 2.50, p = 0.11). A total of 74 children had been diagnosed with at least one other developmental disorder or psychiatric condition, most commonly ADHD, before they received the autism diagnosis. In four children, the autism spectrum disorder was accompanied by an intellectual disability.

Interpretation: Maternal national background appears to be a less significant factor among school-age children than among preschool children who receive an autism spectrum diagnosis, and age at the time of diagnosis should be specified in studies on autism in children and adolescents. Psychiatric comorbidity and other accompanying developmental disorders may suggest shared aetiological factors or increased vulnerability in cases of undiagnosed autism in children.