Study from Sweden: No Real Increase in Prevalence
Sebastian Lundström and colleagues have an article in the BMJ titled "Autism Phenotype Versus Registered Diagnosis in Swedish Children: Prevalence Trends over 10 Years in General Population Samples." The abstract:
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.
Design Population based study.
Setting Child and Adolescent Twin Study and national patient register, Sweden.
Participants 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.
Main outcome measures 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="" br="" 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.
From the article:
We believe that our findings indicate that the prevalence of autism spectrum disorder is not increasing in childhood. The research and clinical resources currently devoted to dealing with these problems relate to the possibly mistaken notion that there is an actual increase. This allocation of specific resources to study “the epidemic of autism” should not be allowed to spiral out of proportion. Other developmental disorders, such as intellectual developmental disorder, language disorder, and attention-deficit/hyperactivity disorder may recently have become overshadowed and seem to be missed diagnoses in many instances, where now only autism spectrum disorder is diagnosed (even perhaps when the autism symptomatology is relatively mild). There is growing evidence that these other developmental disorders are at least as good as or perhaps even better indicators of outcome (and hence, sometimes, need for intervention) as autism spectrum disorder in itself.42Research and clinical practice need to refocus on the child’s overall clinical situation and to acknowledge that autism is but one of the many Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations (ESSENCE).43 Children who are clinically impaired at an early age and who meet the criteria for autism spectrum disorder almost always have other developmental disorders and problems that need to be tackled.44 Clinics specialising in autism spectrum disorder are unlikely to be able to cater to all the needs of affected children and their families.
