Autism Identification Rates Continue to Rise

A CDC report issued shortly before Christmas found that autism rates surged 56% between 2002 and 2006. Coincidentally, 2006 is also the year in which the first drug approval was issued for a pharmaceutical used in the treatment of autism: namely, Risperdal.  This timing suggests that the increase in autism identification over this period was not straightforwardly related to pharmaceutical marketing (potentially excepting off-label marketing during this period). It is also important to note that this latest surge is part of an ongoing increase in the rate of autism diagnosis cast longitudinally over several decades.

The study’s lead author noted in the press that it is difficult to determine how much of the increase is attributable to an actual increase in autism among children, and how much is due to increased rates of detection.  This uncertainty, however, did not preclude speculation about some of the potential environmental causes of the condition presently under investigation, such as “exposure to hazardous pollutants and the added risk of parents giving birth at older ages”.

In the CDC study, children met the case definition for an Autistic Spectrum Disorder if their medical records documented behaviors consistent with DSM-IV-TR criteria for autistic disorder, pervasive developmental disorder–not otherwise specified (PDD NOS), or Asperger disorder. Children were classified as having a previously documented ASD classification if they had 1) received a diagnosis of autistic disorder, PDD-NOS, Asperger syndrome, PDD, or ASD by a qualified professional that was documented in an evaluation record or 2) had received special education services under an autism eligibility category. Reliability of previously documented ASD classifications is not discussed at any length in the report.

What is the social significance of increasing rates of autism identification?  Is this significance affected by whether or not these rates reflect an actual increase in true positives?  Is this trend likely to continue?  And finally, how is this trend likely to be affected by proposed changes to the Autism Spectrum currently under consideration for inclusion in the DSM-V?

CJ Murdoch