The incidence of diagnosed autism spectrum disorders in Finland

AbstractBackground: Previous reports indicate an increase in incidence of autism spectrum disorders (ASD). Aims: First, to assess the incidence of diagnosed ASD in children born between 1996 and 1998, based on nationwide inpatient and outpatient register information. Second, to investigate the incidence rate over time of diagnosed ASD and specifically childhood autism, Asperger's syndrome and pervasive developmental disorder (PDD-NOS) in children born between 1987 and 1998. Methods: This is population-based cohort study with children born in Finland between 1 January 1987 and 31 December 2005; a total of more than 1.2 million children. Children were identified in the Finnish Hospital Discharge Register, and the reported diagnoses were based on the International Statistical Classification of Diseases (ICD-10, ICD-9). Results: The annual incidence rate of diagnosed ASD based on inpatient and outpatient register data was 53.7 per 10,000 (95% CI 50.4–57.2). Incidence was 82.6 per 10,000 in boys and 23.6 per 1...