There are several factors that have been linked to autism. These include genetics, infections in the womb, and inflammation of the nervous system. Various research methods are being used to determine the most likely causes of autism. The most widely used method is called epidemiology, which involves the study of disease frequency in different groups.
Genetics
Recent research has shown that certain genetic variants may be a cause of autism. Researchers have identified loss-of-function variants in four genes that are associated with autism. The variants do not always cause autism, but in people who have autism, they are inherited at higher levels than expected.
The scientists examined whole-genome sequences from 829 families, including autistic individuals and their nonnautistic siblings. The team looked for mutations in noncoding DNA, which regulate gene expression. Because individual DNA base changes in noncoding regions are hard to detect, they looked for structural variants.
While environmental factors have been found to increase the risk of developing autism, these factors are not the cause. People with autism may still be susceptible to environmental risk factors.
Birth defects
In a recent study, researchers found that birth defects may be a possible cause of autism. The findings showed that there was a nearly two-fold increase in the risk of autism among children with various types of birth defects, independent of perinatal and demographic risk factors. The increased risk was comparable to estimates obtained in two other large population-based studies. The magnitude of this increased risk varied with type of birth defect and presence of other developmental disabilities.
Autism is thought to be caused by a combination of genetic and nongenetic influences. In general, most of these influences seem to interfere with important aspects of early brain development, including communication between brain regions and nerve cells. Further research is needed to determine the exact causes of autism.
Infections in the womb
Infections in the womb are thought to increase the risk of developing neurodevelopmental disorders later in life. However, they are not considered a primary cause of autism. A recent study published in The Lancet Psychiatry points out that there may be a connection between infections during pregnancy and autism.
The study examined the records of 1,791,520 children. It looked at hospitalization codes to determine if children were exposed to infections while they were in the womb. The researchers found that there was an increased risk of autism, depression, and mental health disorders in children who had infections during pregnancy. This was true whether or not the infection was a urinary tract infection, or a more severe infection. However, no such association was found in cases of psychosis or severe mental illness.
The study also looked at the effects of infections during pregnancy in sibling pairs. This suggested a weaker connection with autism, but it didn’t rule out the possibility.
Inflammation of the nervous system
While it is unclear which factors trigger autism, it is likely that inflammation plays a role. Inflammation in the womb during pregnancy has been associated with higher risk for autism and children of mothers with chronic conditions linked to inflammation are more likely to develop autism. Inflammation in the mother’s body may also contribute to damage to the fetal brain during early development. The next step in studying this connection is to determine if treating inflammation in children with autism would reduce the symptoms of autism.
Previous studies have identified genes related to inflammation in autism. Mice with autism have a higher level of IL-17a in their brains than mice without the condition. These abnormalities in mice have been linked to altered circuit development and anxiety-related behaviour. However, these findings have not been replicated in humans. However, they suggest that the elevated levels of inflammation may be related to maternal infections in pregnancy.
Environmental factors
Environmental factors are known to affect brain development in children, including those with autism. Research has shown that exposure to pollutants from traffic and other pollution is associated with an increased risk of autism, as is exposure to certain types of pesticides. But the precise cause of autism remains a mystery. Researchers are looking for more information on environmental factors and autism.
In recent decades, the number of children diagnosed with autism spectrum disorder has risen at an alarming rate. The precise etiology of autism remains unknown, but environmental factors are thought to play a role in its onset and progression. In addition, environmental risk factors are preventable, so they are important to address.