Commentary : MMR and Autism in Perspective : the Denmark Story

Autism and related developmental disorders, once rare, are now becoming a common problem in Western countries. Although frequently catastrophic in their effects, the current crisis has come up against a “duck and cover” mentality from many a dusty corner of conventional medical wisdom. Classification of these disorders is symptomatic and owes little to etiologic or pathogenetic considerations. The major classification systems (DSM and ICD) are of extremely limited value – even an impediment – when considering mechanisms of causation. Both systems attempt to handle diagnosis in a discontinuous fashion under the broad umbrella of Pervasive Developmental Disorder (PDD) [Table 1]. With considerable symptomatic overlap between these disorders, there appears to be no biological evidence that they are not, or cannot be, continuous, representing a spectrum of varying phenotypic character and severity, sharing certain common pathogenetic features, genetic polymorphisms, and etiologic origins. The limitations of the symptomatic classification of childhood developmental disorders in general is exemplified by the observation that the now increasingly well characterised intestinal pathology reported in regressive autism has also been described in children whose diagnoses are consistent with autism, childhood disintegrative disorder, attention deficit hyperactivity disorder (ADHD), and Asperger’s syndrome. This suggests an underlying pathogenetic commonality that transcends behavioral descriptors. In summary, rather than helping to resolve the origins of childhood developmental disorders, the diagnostic criteria are artefactual and evanescent. As such, they may serve to confuse by accommodating different interpretations of the same data, such as those coming from Denmark. In this issue, Goldman and Yazbak use data from the Danish Psychiatric Central Register Data (DPCRD) to report prevalence of autism by age category during 1980 to 2002. They show that prevalence of autism among children aged 5-9 years increased from a mean of 8.38/100,000 in the pre-licensure era (1980-1986) to 71.43/100,000 in 2000. After attempting to adjust for the factor (or artefact) of the first study to actually 1-9