Over the past 15 years, the number of children with autism has dramatically increased. When I was in training in California in the 80s, autism was considered rare–occurring in only one of each 10,000 children. Today it is one in every 150 children. Doctors are diagnosing autism at a younger age due to increased awareness of early warning signs such as language and social delay, but only 24 percent of the increase can be explained by earlier diagnosis.

“Diagnostic substitution” is another explanation. As rates of autism increased from 1994 to 2003, the rates of mental retardation and learning disabilities decreased. It is possible that the overall population of children with autism-like characteristics has remained constant, but specific diagnoses within this pool have switched. Some researchers still feel the increase is merely a reporting anomaly.

Causes of autism remain unknown. Genetic factors play a prominent role and have been demonstrated in studies of twins and family members having similar characteristics. New DNA studies found gene duplication or deletions appear to be linked to autism. Still, genetic influences alone cannot account for such a rapid rise in a disorder’s prevalence.

Proposed causal agents include antibiotics, viruses, allergies and enhanced opportunities for parents with mild autistic traits to meet and mate. In one recent study conducted by Cornell University, elevated rates of television viewing by infants have been shown to be a potential link. Few of these explanations have been investigated systematically, and all remain speculative. We do know that premature children or those having conditions such as Tuberous Sclerosis or Fetal Alcohol Syndrome have an increased risk of autism.

Much of the hype surrounding a link between vaccines and autism was fueled in 1998 by British gastroenterologist Andrew Wakefield and his colleagues. However, the results of several large American, European and Japanese studies demonstrate that although the rate of MMR vaccinations has remained constant or declined, the rate of autism diagnoses has soared. In addition, after the Danish government stopped administering thimerosal-bearing vaccines, rates of autism continued to rise.

Many researchers have theorized a pregnant woman’s exposure to chemical pollutants, particularly metals and pesticides, could alter a developing baby’s brain structure, triggering autism. Research is focusing on environmental and genetic causes. In my opinion, like other diseases such as cancer, the cause is one’s genetic predisposition followed by environmental factors that actually produce the symptoms of autism. It has serious effects, not just on an individual child’s health but also on education, health care and the economy.

Don Eastmead, M.D., has been with the Memphis Neurology Group (formally Pediatric Neurology) since 1986.  Dr. Eastmead is a Developmental Pediatrician and specializes in autism, ADHD, learning and behavior disorders.  He graduated from Southwestern Medical School, University of Texas and is board certified in pediatrics.  Dr. Eastmead treats patients at Le Bonheur and his Germantown office.