Autism is one of the most intriguing disabilitating disorder. Historically, autism is considered as a rare disease 2-5 per 10.000. Today prevalence is estimated 20: 10.000. Autism has received significant attention by the public and scientists alike. It is believed that cases of autism has reached an epidemic proportions. As a part of the debate we would like to have a brief description of an article by Dr. Lawrence Scahll, PhD from the Yale University, published in Clinical Psychiatry News.
Dr. Scahll believes that autism is not the epidemic because:
Statistics are increased due to broadening diagnostic category rules for pervasive developmental disorder, better sampling and better diagnostic procedure.
In 1994 DSM IV broadened diagnostic definition for autism and related Asperger’s Disorder and plus Pervasive Developmental Disorder (PDD NOS) – you broaden definition – prevalence is going up.
The issue of sampling – In the past clinicians were counting all known cases identified by clinicians in the field. There was always a gap between identified cases and all cases, this was leading to underestimation. Underestimations was true for depression, ADHD and OCD, The new ways of counting increased prevalence numbers.
Diagnostic precision has improved – In the past it was difficult to differentiate between mental retardation with autism. Now adding lower and higher functioning children with mental retardation and autism were contributing to the rise of newly identified cases.
This conclusion is supported by analysis of data from the March of Dimes Birth Defects Foundation and the California Department of Health Services that conducted a population-based study of birth cohorts from 1987-1994. They found that during that period autism increased from 5.8 to 14.9 per 10 000.
During the same time period the prevalence of mental retardation decreased about the same amount: from 28.8 to 19.5 per 10000(J. Autism Dev. Disorder. 2002, 32: 207-15) This means that many children with mental retardation combined with aoutism moved to the category of “autism” from “mental retardation”.
Too rapid increase in autism even if it is true numbers is difficult to explain by genetics. Environmental causes such as measles, mumps, rubella (MMR) vaccine Thimerosal – proved do not be the real triggers. The Institute of Medicine carefully evaluated all data and found no connections.
The conclusion is that autism is not the new epidemic, but it is still a very important public health issue!
Clinical Psychiatry News, March, 2008