What Causes Autism Spectrum Disorder?
The onset of autism in a child likely occurs long before developmental delays or behaviors emerge, quite possibly before a child is born. For many children, signs of ASD exist from birth and their development is never typical. A smaller percentage of children seem to develop typically. Then, usually between ages 1 and 2, they regress (or appear to lose skills). Children who experience this regression present the most puzzling evidence for a vaccine-autism link. Researchers have investigated the link in these children specifically but still no evidence for a link between autism and vaccines was found.
Scientific Investigations to Date
Scientists have investigated genetics, genomics, environment, gastrointestinal issues, proteins, toxins, diet, immune system, vaccines, maternal stress, paternal age, maternal age, maternal infections, societal changes, television, cell phones, microwaves—and probably a few others. Unfortunately, science has yet to identify a cause with sufficient, robust evidence that will explain ASD.
Genomics, or the study of gene sequences and interactions, present some of the most convincing evidence. While there is no evidence of hereditary factors (passed from previous generations), there is evidence of increased familial risk. That is, if there is an older sibling with ASD, a younger sibling has a higher risk of developing ASD than what we see in the general population. Still, common genetic mutations are often not found among two siblings with the disorder.
Different studies of identical and non-identical twins support both a genetic and an environmental cause of ASD. Currently, more than 400 genes are significantly associated with ASD, but none are found in every person with the disorder. Many people with ASD have no known genetic mutation. In fact, all known genetic mutations combined can only explain about 20% of all the people with ASD today. While genes matter, they are clearly not the whole story.
Focus on Early Intervention and Treatment
As with any disorder, disease, or syndrome, identifying and understanding the cause is important because it may help improve early identification and treatment. However, with a disorder like ASD, its potential causes are probably as diverse as the presentation of the disorder itself. There is so much to learn about how to best help the group of individuals who have ASD today, that at this point, research might better serve the population by first focusing on more effective treatments and then attempting to identify causes as a secondary effort.