Several different genes appear to be implicated in autism spectrum disorder (ASD). For some children, ASD may be associated with a genetic disorder, such as Rett syndrome or fragile X syndrome. For other children, genetic changes (mutations) may increase the risk of ASD. We know that there is no single cause for autism.
Research suggests that autism develops from a combination of genetic and non-genetic, or environmental influences. Autism does not have a single cause, both in terms of genes and the brain. In a minority of cases, there are very clear genetic abnormalities that cause autism. In other cases, genetic differences are more complex and have not yet been discovered.
Scientists believe that both genetics and the environment are likely to play a role in ASD. There is serious concern that autism rates have increased in recent decades without a full explanation as to why. Researchers have identified a number of genes associated with the disorder. Imaging studies of people with ASD have found differences in the development of several regions of the brain.
Studies suggest that ASD could be the result of alterations in normal brain growth very early in development. These alterations can result from defects in genes that control brain development and regulate the way brain cells communicate with each other. Autism is more common in children born prematurely. Environmental factors may also play a role in gene function and development, but specific environmental causes have not yet been identified.
The theory that parental practices are responsible for ASD has long been refuted. Multiple studies have shown that vaccination to prevent childhood infectious diseases does not increase the risk of autism in the population. There is not a single cause of ASD. Many different factors have been identified that may make a child more likely to have ASD, including environmental, biological, and genetic factors.
To this day, scientists and researchers are still investigating the cause of autism spectrum disorder (ASD). After years of studies and exams, it is clear that a single factor may not cause autism. What is clear is that autism is the result of a combination of physical and environmental factors that ultimately affect brain development. People with certain genetic variations are said to be likely to develop autism.
These genes are thought to affect brain development. People with genetic disorders such as fragile X syndrome are at high risk of developing autism. The syndrome, which causes learning disabilities, is one of the many genetic abnormalities that can cause autism. To date, scientists have identified 30 genes involved in the risk of developing autism.
Most of these genes are responsible for brain growth. However, after decades of scientific research, scientists cannot identify a genetic trait that is common in all people with autism. Because some forms of autism are very likely to be caused by genetics, autism can be inherited. For example, twins are likely to have autism and their siblings are likely to be born a few years apart.
This theory was shown to be accurate after the first study of twins in 1977 (Folstein & Rutter, 1977). The study involved 21 pairs of twins, 11 of whom were identical and 10 were fraternal. Identical twins were found to have 36 percent similarity in autism symptoms, while it was zero percent for twins fraternal twins. Because of many important studies on siblings with autism, it is clear that this is an inherited condition.
More studies are needed to answer questions such as how many chromosomes cause autism. According to studies, a parent whose first child has autism has a 10 percent chance of having a second child with autism. This is called the recurrence rate, and parents with an autistic child should be aware of this possibility. It is also possible that a younger brother of a child with autism does not have ASD, but still shows autistic traits, as a recent study found.
The study called Sibling Recurrence and the Genetic Epidemiology of Autism, conducted by Dr John Constantine, professor of Psychiatry and Pediatrics at the University of Washington, found that 26 percent of families had more than one child on the spectrum or had “unaffected siblings who did not develop ASD but diagnosed with other developmental disorders, specifically in language skills. Pregnancy conditions can be considered non-genetic, and some studies suggest that they may affect brain development that can eventually lead to autism. Several studies have concluded that exposure to certain toxic drugs and chemicals during pregnancy can affect brain development and possibly cause autism. Premature birth or babies born before 35 weeks are also at high risk of developing autism later in life.
A recent study found that 26 percent of premature babies developed autism. In addition, viral infections such as rubella during pregnancy can increase the risk of autism in children. Another current study found that women who had gestational diabetes, high blood pressure, abnormal bleeding during pregnancy, and low birth weight at birth are at high risk of having a baby with autism. At this time, there is no test to determine if a pregnant woman's baby will have autism.
However, a promising study conducted at the Rensselaer Polytechnic Institute states that they can predict with 90 percent accuracy whether a mother has a 1.7 percent risk of having a child with autism. Some studies warrant that pregnant mothers use caution when observing their medicines during pregnancy. Medicines that are said to be related to autism include antidepressants, acetaminophen, and asthma medications. Clinical research published in the Archives of General Psychiatry says that taking antidepressants may slightly increase the risk of having a child with autism.
