swiss medicaThe incidence of autism spectrum disorder (ASD) is rising across the world. Several factors have been implicated in increasing the risk of what causes autism. A combination of genetic and environmental factors is believed to play a role in influencing it.
However, researchers have not yet found what is the main cause of autism or one single cause of ASD, making it more challenging to prevent this condition.
Genetic Factors
The risk of autism is higher in kids who have a sibling or parent diagnosed with this condition, suggesting the possible role of genetic factors in the development of this disease. Here is the breakdown of genetic factors that could elevate the influence of autism.
Hereditary Links
Recent research in the field of genetics has revealed that ASD could be genetically linked. The impact of how or what genetics cause autism is established by research that estimated the heritability of ASD to be nearly 80%.
Family History and Genetic Predisposition
Genetic factors, including gene mutations inherited from a parent, can make a child more vulnerable to developing ASD. However, not all children who have parents or siblings with autism develop this disorder. [2]
Researchers have found what genes cause autism or contribute to what causes autism. These variants result in permanent damage to the DNA sequences that make up a gene.
Mutations and Copy Number Variations
Several genetic mutations and variations are being studied for their possible role in the development of ASD. For example, copy number variations including the duplication and deletion of certain genes in chromosome 22 are strongly linked to the risk of ASD.
Role of De Novo Mutations
De novo mutations refer to genetic alterations that appear in a person of the family for the first time without any reported occurrence of the mutation in the earlier generations. Recent research reveals that de novo mutations contribute to nearly 52 to 67% of cases of what causes autism disorder in low-risk families.
Chromosomal Changes and Their Impact
Genetic mutations arising as a result of changes in the sequence of DNA and abnormalities related to chromosomes can significantly affect the growth and development of a child, making him vulnerable to developing autism.
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Environmental Influences
Several environmental factors, including very low birth weight, higher parental age at the time of conception, a history of infections and medications during pregnancy, and maternal obesity, are believed to play a role in increasing the risk of autism in a child.
Prenatal Factors
Here are some parental factors that can elevate the risk of autism in a child.
Maternal Health and Nutrition
Eating a healthy and nutritious diet or using nutritional supplements can lower the influence of what causes autism in pregnancy and reduce the risk of autism in a child. For example, the use of folic acid supplements before and during pregnancy significantly reduces the risk of having a child with autism.
Exposure to Environmental Toxins
A history of exposure to environmental toxins before and during pregnancy can significantly elevate the risk of autism in the child.
Complications During Pregnancy
Unfavorable events and complications include what causes autism during pregnancy. These events can make the child more vulnerable to developing ASD. For example, there is evidence establishing the association between the history of fever and infectious diseases during pregnancy and ASD in the child.
Perinatal Factors
Here are some perinatal factors that can influence the risk of autism in a child.
Birth Complications and Stressors
Birth complications that can increase the risk of ASD include:
- Abnormal fetal presentation
- Fetal distress
- Birth trauma
- Multiple births
- Umbilical cord complications
- Low birth weight
- Maternal hemorrhage
- Low 5-min Apgar score
- Small for gestational age
- Meconium aspiration
- Neonatal anemia
- ABO or Rh incompatibility
Oxygen Deprivation and Neurodevelopmental Impact
Oxygen deprivation during childbirth is not known to directly affect the development of the brain and nervous system in the child and cause autism. However, it is believed to potentially elevate the risk of ASD in the presence of genetic susceptibility factors such as a family history of autism.
Postnatal Influences
Here are some postnatal influences that are associated with a higher risk of autism.
Impact of Parental Age
Evidence suggests that a higher parental age at the time of conception could elevate the risk of autism in a child. Parents in their 40s have nearly 5 to 10 percent higher chances of having a child with autism compared to 20-year-old parents.
Neurological and Brain Development
Neurological problems that influence the development of the brain and nervous system can contribute to what causes autism, especially in children with a family history of this condition.
Abnormalities in Brain Structure
Some brain structures that show abnormalities in children with autism include:
- Midbrain
- Pontine
- Left parahippocampal gyrus
- Bilateral hippocampus
- Left middle temporal gyrus
- Left superior occipital gyrus
- Left superior temporal gyrus
- Left temporal pole
Differences in Brain Size and Connectivity
What causes autism in the brain is also connected to the brain size. Autistic children typically have a faster expansion of the surface area in the cortical region of the brain between 6 and 12 months of age compared to non-autistic children of the same age. The brain volume is also found to increase much faster in children with autism in the second year of life.
Role of Neurotransmitters
Disruption in the secretion of neurotransmitters in the brain could contribute to the development of autism in some children. These disruptions are more likely to be caused by genetic mutations.
Altered Synaptic Function
Synaptic dysfunctions can interfere with the normal functions of the brain and nerves, leading to emotional and behavioral challenges associated with autism. The altered synaptic function can also play a role in triggering certain physical symptoms associated with autism, especially repetitive behaviors like the flapping of hands.
Disruptions in Communication Between Neurons
Changes in the levels of neurotransmitters in the brain can cause disruptions in the communication between neurons, due to which a child may develop physical and behavioral symptoms of autism, such as
- Sensory hypersensitivity to touch, smell, and sound
- Repetitive or ritualistic behavior
- Aggression
- Repeating certain phrases or words
Impact on Information Processing
Genetic mutations and structural changes in the brain can affect the cognitive functions of the child. As a result, the child may have difficulties related to information processing, which is typically noted in the form of inability to learn new skills, poor academic performance, low memory, and reduced attention span.
Immunological Factors
Some immunological factors can trigger the development of autism or worsen the symptoms of this condition.
Inflammatory Responses
Children with autism are likely to have a higher level of inflammation in the body, suggesting the role of chronic inflammatory damage in the progression of this condition. They are also likely to have a higher level of pro-inflammatory compounds, such as cytokines, released by the immune cells.
Immune System Dysregulation
Disruptions in the activities of the immune system associated with allergies, autoimmunity, and food sensitivities or intolerances are suspected to play a role in the progression of autism.
Maternal Immune Activation
The incidence of autism is higher in children born to mothers diagnosed with autoimmune disorders, indicating the possible role of maternal immune activation in the development of disease.
Autoimmune Connections
Autoimmune conditions, both in the mother and the child, can contribute to the faster progression of autism. Autoimmune conditions that are strongly associated with what causes autism in pregnancy include Sjögren’s syndrome and rheumatoid arthritis.
Immunological Disorders and Autism
The prevalence of autism is significantly higher in children whose parents or siblings have immunological dysfunctions such as allergies or autoimmune disorders.
The Interplay Between Immune System and Neurodevelopment
The higher prevalence of autism in children with immune system dysfunction is linked to the role of the immune system in the development of the nervous system.
Intersection of Genetic and Environmental Factors
As we see, there is no single primary cause of autism spectrum disorder. Some genetic and environmental factors worsen the pre-existing immunological dysfunctions, making a child more vulnerable to developing ASD.
Gene-Environment Interactions
The adverse impact of genetic and environmental factors tends to worsen further in the presence of immunological dysfunctions. This poses challenges in the management of this condition.
Complex Interplay in Autism Etiology
The etiology of autism encompasses a complex interplay between a combination of genetic and environmental factors, maternal factors, and immunological and neurological dysfunctions. The history of adverse childhood events and structural changes in the brain are likely to increase the risk of what causes autism further.
The Role of Epigenetics
Epigenetics is believed to play a significant role in influencing the risk of autism in children.
Epigenetic Modifications
Epigenetic modifications associated with 5-methyl-tetrahydrofolate, which is a methyl donor for DNA methylation, can influence the development of autism. Similarly, changes in folate metabolism could affect DNA methylation and contribute to what causes autism.
Environmental Impact on Gene Expression
Environmental factors may induce alterations in gene expression and contribute to the risk of autism. For example, maternal and environmental factors can induce alterations in the microglia gene expression due to which the child may develop ASD. Further research is expected to provide more insights into what is causing a rise in autism.
Potential Reversibility and Intervention
There is ongoing research to investigate the potential reversibility of environmental factors in the development and progression of autism and what causes autism regression. Further research in the fundamentals of epigenetics is expected to offer promising interventions that could potentially reverse the impact of environmental factors and lower the risk of autism in children.
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