Background: The prevalence of autism spectrum disorders (ASD) has increased 10-fold in recent years. We have assessed the prevalence of high functioning autism spectrum disorders in a clinical sample in a Norwegian county.
Material and method: Medical records from the health specialist services were assessed for children (0-18 years of age) with a diagnosis of Asperger syndrome or pervasive developmental disorder not otherwise specified (PDD-NOS) in South Trøndelag county at two time-points (1.1.2005 and 1.1.2008). We also estimated the prevalence of high functioning children with autism (HFA) 1.1.2008.
Results: The number of children and adolescents with the diagnosis Asperger syndrome increased from 70 in 2005 to 121 in 2008 and that for children with PDD-NOS increased from 22 to 44 in the same period. In the child mental health service, the number of patients with Asperger syndrome increased from 51 in 2005 to 99 in 2008 and in the habilitation services there were 32 such patients in both years assessed. Some patients were registered in both services: 13 in 2005 and 10 in 2008. In 2008, the prevalence of all high functioning autism spectrum disorders together was 0.35 % of the population in the age 5-18 years. Almost none of the children were below 5 years at the time of assessment.
Interpretation: In South Trøndelag the prevalence of children with high functioning autism spectrum disorders are in the same size order as that reported from international surveys. This can be explained by increased awareness on such disorders and that more able people are diagnosed. The difference in prevalence between the health services reflects different diagnostic traditions and changed referral routines.