Autism phenotype versus registered diagnosis in Swedish children: prevalence trends over 10 years in general population samples.
OBJECTIVE
To compare the annual prevalence of the autism symptom phenotype and of registered diagnoses for autism spectrum disorder during a 10 year period in children.


METHODS
Population based study.


METHODS
Child and Adolescent Twin Study and national patient register, Sweden.


METHODS
19, 993 twins (190 with autism spectrum disorder) and all children (n=1,078,975; 4620 with autism spectrum disorder) born in Sweden over a 10 year period from 1993 to 2002.


METHODS
Annual prevalence of the autism symptom phenotype (that is, symptoms on which the diagnostic criteria are based) assessed by a validated parental telephone interview (the Autism-Tics, ADHD and other Comorbidities inventory), and annual prevalence of reported diagnoses of autism spectrum disorder in the national patient register.


RESULTS
The annual prevalence of the autism symptom phenotype was stable during the 10 year period (P=0.87 for linear time trend). In contrast, there was a monotonic significant increase in prevalence of registered diagnoses of autism spectrum disorder in the national patient register (P<0.001 for linear trend).


CONCLUSIONS
The prevalence of the autism symptom phenotype has remained stable in children in Sweden while the official prevalence for registered, clinically diagnosed, autism spectrum disorder has increased substantially. This suggests that administrative changes, affecting the registered prevalence, rather than secular factors affecting the pathogenesis, are important for the increase in reported prevalence of autism spectrum disorder.
Gillberg Neuropsychiatry Centre, University of Gothenburg, Kungsgatan 12, 411 19, Gothenburg, Sweden Centre for Ethics, Law and Mental Health, University of Gothenburg, Sweden sebastian.lundstrom@gnc.gu.se.
Sebastian
S
Lundström
Departments of Psychiatry and Preventive Medicine, Mount Sinai School of Medicine, New York, NY, USA.
Abraham
A
Reichenberg
Centre for Ethics, Law and Mental Health, University of Gothenburg, Sweden.
Henrik
H
Anckarsäter
Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Paul
P
Lichtenstein
Gillberg Neuropsychiatry Centre, University of Gothenburg, Kungsgatan 12, 411 19, Gothenburg, Sweden.
Christopher
C
Gillberg
D000293:Adolescent; D001321:Autistic Disorder / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics; D002648:Child; D003937:Diagnosis, Differential; D004200:Diseases in Twins; D005260:Female; D005544:Forecasting; D006801:Humans; D008297:Male; D010290:Parents; D010641:Phenotype; D011159:Population Surveillance / Q000379:methods*; D015995:Prevalence; D012042:Registries; D013548:Sweden / Q000453:epidemiology; D014427:Twins