What Causes Autism?...continued
No one is sure what causes autism. Through twin studies, scientists have determined that autism is a genetically based condition. If one identical (monozygotic) twin has autism then there is an 80-90% chance that the other twin will also be diagnosed with an autism spectrum disorder. For non-identical (dizygotic) twins there is a 3-10% chance that both twins will develop autism spectrum disorder. The chance that siblings will both be affected by ASD is also approximately 3-10%.
Scientists are unsure what, if any, environmental triggers may be involved in autism. One theory popular in the late 1990s and early 2000s, that vaccines may cause autism, has since been disproven by numerous studies conducted in multiple labs around the world.
Autism Science Foundation
Genetic inheritance is involved in the development of autism spectrum disorders. Genetic factors likely interact with environmental variables to result in the expression of autism. Neurobiological research indicates that autism is likely the result of genetically determined abnormalities in brain development. This abnormal brain development may start before the child is born. It has been difficult for genetics researchers to locate a specific chromosome(s) involved in autism but recent studies have led to some promising results such as potentially identifying a susceptibility gene.
The New England Center for Children
Many autism cases occur in families with a history of ASD or related disabilities. Research also suggests that some children may be born with a susceptibility to ASD, but a single “trigger” that causes the disorder to develop has not been identified. A variety of factors could be associated with some forms of ASD, including viral infections, problems during pregnancy or delivery, metabolic imbalances and exposure to environmental chemicals. It is clear that “bad parenting” does not cause ASD. Genetic factors and brain abnormalities at birth are considered to be the most recognized causes, but experts believe genetic and environmental factors probably interact in complex ways to contribute to the onset of the disorder.
Autism spectrum disorders have many biologic causes and many possible outcomes. Some children may improve over time to the extent that they might no longer meet diagnostic criteria for the disorder. Studies have found 3 percent to 25 percent of children improve fully and no longer are diagnosed as having autism. However, they maycontinue to have other developmental and behavioral symptoms. The children who improve are likely to have good learning abilities and to have received behavioral therapy.
American Academy of Pediatrics
Autism by the Numbers
A new government survey estimates that more U.S. children than ever have a diagnosed autism spectrum disorder. Overall, the prevalence was 110 out of every 10,000 children ages 3 to 17. But the rate varied by sex and racial or ethnic group:
Boys: 173 of 10,000
Girls: 43 of 10,000
Hispanic: 103 of 10,000
Non-Hispanic white: 125 of 10,000
Non-Hispanic black: 61 of 10,000
Non-Hispanic multiracial: 71 of 10,000
Non-Hispanic other single race: 66 of 10,000
• It is estimated that between 1 in 80 and 1 in 240 with an average of 1 in 110 children in the United States have an ASD.
• ASDs are reported to occur in all racial, ethnic, and socioeconomic groups, yet are on average 4 to 5 times more likely to occur in boys than in girls. However, we need more information on some less studied populations and regions around the world.
• If 4 million children are born in the United States every year, approximately 36,500 children will eventually be diagnosed with an ASD.
Assuming the prevalence rate has been constant over the past two decades, we can estimate that about 730,000 individuals between the ages of 0 to 21 have an ASD.
The prevalence increase raises “a lot of questions about how we are preparing in terms of housing, employment, social support—all the issues that many of these people (with ASD) are going to need,” said Dr. Tom Insel, director of the National Institute of Mental Health. “It also raises questions about how well we’re prepared in the educational system to provide for the special needs of many of these kids.” Currently, the Autism Society estimates that the lifetime cost of caring for a child with autism ranges from $3.5 million to $5 million, and that the United States is facing almost $90 billion annually in costs for autism (this figure includes research, insurance costs and non-covered expenses, Medicaid waivers for autism, educational spending, housing, transportation, employment, in addition to related therapeutic services and caregiver costs).
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