According to the Centers for Disease Control, 1 in 88 children will be diagnosed with an autism spectrum disorder (ASD) — a ten-fold increase over just four decades. ASD affects two million Americans, and according to Autism Speaks, that's more than the number of children affected by diabetes, AIDS, cancer, cerebral palsy, cystic fibrosis, muscular dystrophy or Down syndrome, combined.
Now that we know that autism is not linked to vaccines, parents are wondering just what the cause could be. While there is no single determining cause of autism, researchers are finding that a combination of genetic and environmental factors play a role in the development of ASD.
Scientists have identified 33 autism gene mutations. Twenty-two of them are newly-identified, and many are spontaneous rather than inherited. As reported to ScienceDaily on April 19, James Gusella, PhD, director of the Massachusetts General Hospital Center for Human Genetic Research says,
"We identified the precise points where the DNA strands are disrupted and segments exchanged within or between chromosomes. As a result, we were able to discover a series of genes that have a strong individual impact on these disorders."
In addition, ScienceDaily reports that balanced chromosome abnormalities (BCAs), in which DNA segments are moved within the same chromosome or exchanged with segments in a different chromosome, are known to be drastically more common in those with ASD. However, according to AutismSpeaks.org, a science and advocacy organization dedicated to preventing and treating autism, a specific gene can be identified as the cause of autism in only about 15% of the patients.
In the presence of genetic mutations, certain environmental factors have been found to increase the risk of autism. These factors include toxic chemicals, viral infections and illness of the mother during pregnancy, and difficulties during birth. According to Autism Speaks, there is a small body of research showing that children whose mothers took prenatal vitamins with folic acid in the months prior to conception as well as during pregnancy had a lowered risk of autism.
In addition to genetic mutations and environmental influences, certain risk factors can increase a child's chances of developing ASD. Male children are three to four more times likely to develop autism according to Autism Speaks, despite the fact that girls with autism tend to have more mutated genes than boys with autism, indicating that the female brain is less susceptible to the autism gene mutations. In addition, families who have one child with autism are more likely to have a second child with autism, and children who have disorders such as fragile X syndrome, tuberous sclerosis, Tourette syndrome, and epilepsy are also more likely to have autism. And finally, children whose parents are older at the time of conception are also at a higher risk of having ASD.
Based on research study findings, a specific cause for autism may not exist. It appears that a combination of contributing factors determines the type of ASD and severity in each individual. However, being aware of the risk factors, possible environmental causes, and the symptoms of autism can help parents better care for their children.