Prevalence of Autism in Scandinavian Countries (Denmark, Norway, Sweden), and Nordic Countries (Finland, Iceland, the Faroe Islands, and Greenland).

Aim: This study aims to identify and describe prevalence rates for ASD in the Scandinavian countries (Denmark, Norway, Sweden), as well as the Nordic countries (Finland, Iceland, the Faroe Islands, and Greenland). Methods: A systematic review was conducted following PRISMA (2009) guidelines and based on the two databases: APA PsycINFO and MEDLINE (PubMed). Results: A total of 13 studies were included in the analyses. It was not possible to identify ASD prevalence studies for Greenland. However, for the remaining countries descriptive increases in ASD prevalence figures were observed. Increases were evident both in relation to age and birth cohort. Studies varied regarding which age group and cohort prevalence figures were reported. The most reported age group was the 7-12-year-olds. In this group, recent prevalence figures for Denmark ranged from 0.26% to 1.47%, in Norway 0.6%, in Sweden 0.23-0.68%, in Finland 0.22-0.86%, and in Iceland 2.40-3.13%. Iceland stood out in terms of higher prevalence figures compared to the other Scandinavian and Nordic countries. Two studies from the Faroe Islands reported ASD prevalence rates between 0.50% and 0.94% for 7-24-year-olds. These studies were based on nationwide figures, but not from national or official registers. Discussion and conclusion: This study documented increasing prevalence of ASD in Scandinavian and Nordic countries. Several explanations of aspects that may contribute to the increases were discussed, eg, heightened awareness of ASD and earlier diagnosis. The importance of considering differences in data sources was discussed, with an emphasis on the importance of using national registries when available as this source is the most reliable and valid. The absence of prevalence figures for Greenland may be attributed to structural as well as cultural aspects, eg, two parallel systems assessing ASD, cultural taboos as well as lack of awareness of ASD. Suggestions or how to gain knowledge on ASD prevalence in Greenland is presented.