Dr. Roxanne Dryden-Edwards is an adult, child, and adolescent psychiatrist. She is a former Chair of the Committee on Developmental Disabilities for the American Psychiatric Association, Assistant Professor of Psychiatry at Johns Hopkins Hospital in Baltimore, Maryland, and Medical Director of the National Center for Children and Families in Bethesda, Maryland.
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
Although autism is the result of a neurologic abnormality, the cause of these problems with the nervous system is unknown in most cases. Research findings indicate a strong genetic component. Most likely, environmental, immunologic, and metabolic factors also influence the development of the disorder.
There is probably no single gene or genetic defect
that is responsible for autism. Researchers suspect that there are a number of
different genes that, when combined together, increase the risk of getting
autism. In families with one child with autism, the risk of having another
child with autism is 3% to 8%. The concordance of autism in monozygotic twins is
30%. A number of studies have found that first-degree relatives of children
with autism also have an increased risk of autism spectrum disorders.
In some children, autism is linked to an underlying medical condition. Examples include metabolic disorders (untreated phenylketonuria [PKU]), congenital infections (rubella, cytomegalovirus [CMV], toxoplasmosis), genetic disorders (fragile X syndrome,
tuberous sclerosis), developmental brain abnormalities (microcephaly, macrocephaly, cerebral dysgenesis), and neurologic disorders acquired after birth (lead encephalopathy,
These medical disorders alone do not cause autism as most children with these
conditions do not have autism.
Environmental factors and exposures may interact with genetic factors to cause an increased risk of autism in some families.
Over time, many different theories have been proposed about what causes autism. Some of these theories are no longer accepted, however.
Emotional trauma: Some believed that emotional trauma
at an early age, especially bad parenting, was to blame. This theory has been
Vaccines: Although the mercury preservative used in some
vaccines is known to be neurotoxic, the most recent research on this subject does not suggest a specific link between vaccines and autism.
Autism is a condition that manifests in early childhoodand is characterized by qualitative abnormalities in social interactions, marked aberrant communication skills, and restricted repetitive and stereotyped behaviors.