A question that confuses all the parents is the cause of autism for their child. Even though proper care is given during the pregnancy, many kids are under the spectrum. A recent survey of parents suggests that 1 in 45 children, ages 3 through 17, have been diagnosed with autism spectrum disorder (ASD). This is notably higher than the official government estimate of 1 in 68 American children with autism, by the Centers for Disease Control and Prevention (CDC).
Causes of Autism were proposed by many but still understanding the theory of causation of autism spectrum disorders is incomplete.The exact cause of autism cannot be identified in most of the children with autism.Research shows that genetic factors predominate. The heritability of autism, however, is complex, and it is typically not clear which genes are responsible for the cause. In rare cases, autism is highly associated with agents that cause birth defects. few other causes have been proposed, such as childhood immunizations, but numerous epidemiological studies have shown that there is no scientific evidence supporting any link between vaccinations and autism.
There is increasing suspicion among researchers that it’s not a single cause but is instead a complex disorder with a set of core aspects that have different causes. Different underlying brain dysfunctions are hypothesized to lead to the common symptoms of autism, just as totally different brain problems result in intellectual incapacity. However, in spite of the strong heritability, most of the cases of ASD occur hardly with no recent evidence of family history.
Following are few causes that are assumed as a leading factor for Autism
Prenatal environment: Few risk factors like diabetes, bleeding, advanced age in either parent and use of psychiatric drugs during the pregnancy are considered as risk factors of Autism.
Infectious processes: Prenatal viral infection is another principal non-genetic cause of autism. Prenatal exposure to rubella or cytomegalovirus activates the mother’s immune response and greatly increase the risk of autism.
Birth defects are caused by environmental agents like Teratogens. Some agents that are theorized to cause birth defects are also been suggested as a danger to autism, although there is little or no scientific evidence to back such claims. These include exposure of the embryo to valproic acid, paracetamol, thalidomide or misoprostol. These cases are rare.
Other maternal conditions: Maternal problems like Thyroid, Maternal Diabetes, and Maternal obesity during pregnancy may also increase the risk of autism, although further study is needed.
Prenatal stress, consisting of exposure to life events or environmental factors that distress an expectant mother, has been hypothesized to contribute to autism, possibly as part of a gene-environment interaction.
Other in utero: It has been hypothesized that folic acid taken during pregnancy may play a role in reducing cases of autism by modulating gene expression through an epigenetic mechanism. This hypothesis is supported by multiple studies. Some research suggests that maternal exposure to selective serotonin reuptake inhibitors during pregnancy is associated with an increased risk of autism, but it remains unclear whether there is a causal link between the two.
Amygdala neurons: Early developmental failure involving the amygdala cascades on the development of cortical areas that mediate social perception in the visual domain may cause in autism. Autoimmune disease: Autoantibodies that target the brain or elements of brain metabolism may cause or exacerbate autism.
Endogenous opiate precursor theory: Autism can be caused by a digestive disorder present from birth which causes gluten and casein to be converted to the opioid peptides gliadorphin (aka gluteomorphin) and casomorphin.
Gastrointestinal connection: Parents have reported gastrointestinal (GI) disturbances in autistic children, and several studies have investigated possible associations between autism and the gut, but the results so far are inconclusive.
Lack of Vitamin D:There is limited evidence for the hypothesis that vitamin D deficiency has a role in autism, and it may be biologically plausible, but more research is needed.
Lead: Lead poisoning has been suggested as a possible risk factor for autism, as the lead blood levels of autistic children have been reported to be significantly higher than typical.
Locus coeruleus–noradrenergic system: This theory hypothesizes that autistic behaviors depend at least in part on a developmental dysregulation that results in impaired function of the locus coeruleus–noradrenergic (LC-NA) system.
Mercury: This theory hypothesizes that autism is associated with mercury poisoning, based on perceived similarity of symptoms and reports of mercury or its biomarkers in some autistic children. But a meta-analysis published in 2007 concluded that there was no link between mercury and autism.
Oxidative stress: This theory hypothesizes that toxicity and oxidative stress may cause autism in some
cases. Evidence includes genetic effects on metabolic pathways, reduced antioxidant capacity, enzyme changes, and enhanced biomarkers for oxidative stress; however, the overall evidence is weaker than it is for involvement oxidative stress with disorders such as schizophrenia.
Refrigerator mother: Child psychologist Bruno Bettelheim believed that autism was linked to early childhood trauma, and his work was highly influential for decades both in the medical and popular spheres.
Vaccines: Scientific studies have refuted a causal relationship between vaccinations and autism. Despite this, some parents believe that vaccinations cause autism and therefore delay or avoid immunizing their children under the “vaccine overload” hypothesis that giving many vaccines at once may overwhelm a child’s immune system and lead to autism, even though this hypothesis has no scientific evidence and is biologically implausible. Because diseases such as measles can cause severe disabilities and death, the risk of death or disability for an unvaccinated child is higher than the risk for a child who has been vaccinated.
MMR vaccine: The MMR vaccine hypothesis of autism is one of the most extensively debated hypothesis regarding the origins of autism. Several studies were conducted based on this and The Centers for Disease Control and Prevention, the Institute of Medicine of the National Academy of Sciences, and the U.K. National Health Service have all concluded that there is no evidence of a link between the MMR vaccine and autism.
Viral infection: Many studies have presented evidence for and against the association of autism with the viral infection after birth. Laboratory rats infected with Borna disease virus show some symptoms similar to those of autism but blood Studies of autistic children show no evidence of infection by this virus. Members of the herpes virus family may have a role in autism, but the evidence so far is anecdotal. Viruses have long been suspected as triggers for immune-mediated diseases such as multiple sclerosis but showing a direct role for viral causation is difficult in those diseases, and mechanisms, whereby viral infections could lead to autism, are speculative.
Even though there are many assumptions, the exact and real cause of Autism is yet to identify. Thanks for reading this blog and kindly contact Be Change Centre for Autism for any questions or visit our centre in Marathahalli, Bangalore. We encourage you to visit our website frequently as we will be adding many more informative articles.