Causes Of Asperger Syndrome

The causes of Asperger Syndrome are not fully understood yet. It is believed that genetics, environment & brain function may play a crucial role in the development. However, poor parenting or upbringing of a child may not be considered as influencing factors.

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Understanding Asperger Syndrome

Asperger syndrome or Asperger’s Syndrome (AS) was originally introduced in 1981 by English psychiatrist Lorna Wing. The name is derived from a study published by Austrian paediatrician Hans Asperger in 1944. According to a 2019 research paper, Asperger’s is a type of autism spectrum disorders (ASDs) “referring to various milder forms of autism.” Studies 1 show that AS is more common in boys than girls with a male to female ratio of 4:1 and a “minimum prevalence of 3.6 per 1.000 children,” within the 7 to 16 years age range.

However, like other ASDs the exact causes for the onset of this neurodevelopmental disorder has not yet been identified. The condition tends to be highly complex in nature and the severity of symptoms vary greatly from one person to another. Hence, it is believed that there may be a number of probable factors that may cause the development of this disorder. Experts believe that genetics, environmental factors and brain abnormalities may play a key role. Moreover, certain risk factors can also increase the likelihood of a person developing the condition.

Causes Of Asperger Syndrome

Experts have managed to identify some potential factors that may influence the development of Asperger’s. Here are some of the most common factors that need to be considered:

1. Genetics

According to a study 2 , “Although the importance of genetic factors in the transmission of autism is increasingly clear it also appears that genetic factors may play an even more important role in Asperger syndrome (AS).” Hence, the condition may run in families as there may be a prominent genetic basis 3 and is highly heritable 4. However, inheritance of the condition may be a complicated process. According to a 2007 study 5 , “Twin and family studies have indicated that genetic factors play a significant role in the development of ASD,” including Asperger’s, “in a complicated fashion of inheritance.” As environment and other factors influence the development of the syndrome, the impact of genetic predisposition is yet to be understood. Different population studies 6 have found evidence related to the genetic basis of autism spectrum disorders. A 2016 study 7 found that research has consistently found “a clear genetic etiology of ASD.” However, it may also have a “multifactorial etiology” as both genetics and environment play an important role. However, it has been observed that genetic factors play “the largest role.” The study adds “Clinical genetic evaluations currently can identify the cause of ASD in 30%-40% of cases.”

According to a 2006 study 8 of twins, heritability for autism spectrum disorders was estimated to be more than 90%. However, recent research 9 based on twin studies shows that heritability estimate may be from 60%-90%. However, heritability of Asperger syndrome is not limited only to twins as family members can also inherit the disorder. Research indicates that later-born or younger siblings of children with ASD are more likely to develop the disorder. One 2011 study 10 explains “First-degree relatives of ASD probands have an increase in behavioral or cognitive features associated with autism, such as social or language dysfunction, albeit in lesser forms, when compared with the population prevalence.” This is known as “the broader phenotype 11 “and may involve restrictive repetitive behaviors, language dysfunction and deficits in social cognition.

For some children, genetic mutations and changes can increase the likelihood of developing Asperger syndrome or others ASDs. Certain genetic mutations may also impact brain development and how brain cells interact, influencing the intensity of symptoms. Apart from inherited genetic factors, spontaneous gene mutations may also occur due to unknown causes and increase the risk of Asperger’s in a child.

Identifying Genes

It is believed that a number of different genes are associated with the development of Asperger syndrome, a subtype of ASD. According to a 2013 study 12 , genetic variation in GABRB3 genes may be related to Asperger’s and autism spectrum conditions (ASC). The study explains that research “confirms the role of GABRB3 as an important candidate gene in both ASC and normative variation in related endophenotypes.” A 2010 study 13 found that Asperger disorder (ASP) “shares both ASD-related genetic risk factors, as well as has genetic risk factors unique to the ASP phenotype.” According to another 2015 study 14 , a mutation in the aryl-hydrocarbon receptor nuclear translocator 2 (ARNT2) gene, associated with neurodevelopmental processes, has been observed in individuals with Autism Spectrum Conditions (ASC) and Asperger Syndrome (AS). Experts believe that there may be various other genes related with an increased risk for Asperger’s.

Different Genetic Conditions

For some sufferers, autism spectrum disorder may be related to particular genetic conditions, like Rett syndrome 15 & Fragile X syndrome. Rett syndrome is categorized as an autism spectrum disorder and is a neurodevelopmental disorder. Often misdiagnosed 15 as infantile autistic syndrome, Rett syndrome and autism are characterized by early onset, lack of typical developmental progress and “absence of progressive deterioration and neurobiologically by fundamental failure of normal neuronal maturation and absence of progressive neuronal or glial pathology,” according to a 2011 study 16 . Moreover, Fragile X Syndrome (FXS 17 ), also known as Martin-Bell syndrome, is perhaps the most popular single-gene disorder. “FXS is the most prevalent inherited cause of mild to severe intellectual disability and the most common monogenic cause of autism spectrum disorder (ASD),” explains a scientific review 18 .

Scientists are currently conducting further research to better understand how different gene variations may influence the development of this condition.

2. Environmental factors

One 2012 study 19 explains that “autism is a complex disorder resulting from the combination of genetic and environmental factors.” Research 20 shows that around 40%–50% of variance in ASD liability are influenced by environmental factors. It is believed that certain environmental factors, like air pollutants, toxins, chemicals, viral infections and medications, can play a crucial role in the onset of Asperger syndrome. Moreover, complications during pregnancy 21 may also be a triggering factor. However, this has not been confirmed by researchers yet. According to a 2017 study 22 , when someone is exposed to harmful environmental elements, then “the expression of developmental key genes” can change in crucial periods of embryo formation and increases the likelihood of genomic imprinting diseases, like autism and Asperger’s. The study explains that as the condition is an epigenetic disorder where environmental risk factors are considered as “the most momentous mediators in its pathogenesis,” identifying these factors can help someone to avoid the onset of autism.

Investigations have shown that perinatal factors and obstetric complications are also associated with ASD. “The increased prevalence of obstetric complications among autism cases is most likely due to the underlying genetic factors or an interaction of these factors with the environment,” explain researchers 23 . However, autism spectrum disorders are typically influenced by a collection of environmental factors 24 instead of only one of them. One 2017 study identified a number of chemical and physiological risk factors that were observed constantly in ASD patients, such as –

  • Traffic-related air pollutants
  • Advanced parental age
  • Preterm or premature birth
  • Low birth weight
  • Hyperbilirubinemia or neonatal jaundice
  • Clustering of pregnancy complications
  • Maternal immigrant status
  • Prenatal viral infection
  • Prenatal and perinatal stress
  • Maternal diabetes
  • Abnormal melatonin synthesis
  • Zinc deficiency
  • Heavy metal poisoning by lead & mercury
  • Gastrointestinal abnormalities

Another 2019 study 25 found that several environmental factors can increase the risk of Asperger syndrome, namely “advanced parental age, assisted reproductive technologies, nutritional factors, maternal infections and diseases, environmental chemicals and toxicants, and medications, as well as some other conditions.” According to another 2007 study 26 , the environmental factors in Asperger’s may not be able to “influence the core social deficits” of the condition. However, these may facilitate the development of other symptoms, like persecutory delusions, anxiety, depression, dissociation, antisocial behavior and criminal behavior.

3. Brain abnormalities

Research shows that brain abnormalities may also be related to the development of Asperger syndrome. Researchers have found that individuals suffering from Asperger’s tend to have brain anatomy differences based on age and may involve structural abnormalities in the cerebellum and fronto‐striatal systems. “We suggest that Asperger’s syndrome probably arises from a generalized abnormality in brain development (causing widespread white matter abnormalities),” add the researchers. It is also believed that such neurodevelopmental abnormalities may be caused by environmental factors, like isolation. Neuroimaging 27 studies have shown structural and functional brain development abnormalities 27 in patients. Moreover, abnormal brain maturation during early childhood and adolescence may also be associated with ASD. According to a 2011 study 28 , “Autism is marked by overgrowth of the brain at the earliest ages but not at older ages when decreases in structural volumes and neuron numbers are observed instead.” Potential reduction in volumetric capacity of the brain and arrested growth have also been observed in some patients after the age of 10-15 years.

Studies 29 show that abnormal brain developmental processes tend to occur early in the clinical course of autism and Asperger syndrome, especially in young children. A 2009 study 30 which mapped brain abnormalities in boys with autism found they had notably enlarged frontal lobes. Moreover, autistic children had significantly enlarged other lobes in the brain. The study also found substantial gray matter volume deficits in bilateral parietal, left occipital and left temporal lobes. A research paper published in 2011 identified certain prominent “clusters of convergence” pointing towards brain abnormalities in sufferers, including-

  • The lateral occipital lobe
  • The pericentral region
  • The medial temporal lobe
  • The basal ganglia
  • Proximate to the right parietal operculum

“Anomalies of brain structure have repeatedly been hypothesized to play a major role in the etiopathogenesis of the disorder,” but the “etiopathogenesis of autism spectrum disorders still remains to be clarified,” states the research paper.

Treatment Can Help

Understanding the causes of Asperger syndrome can help the sufferer or the parents to seek treatment effectively. Although there is no specific cure for the disorder, early diagnosis and treatment can help a child to live a healthy, independent and productive life when they grow up. By learning about the causes of AS, parents and caregivers can develop a deeper understanding and provide better support. This will enable caregivers to help the patient develop helpful coping strategies and prevent social withdrawal and isolation in the patient.

If you or a loved one is suffering from Asperger’s, then make sure to consult a doctor immediately.

References:
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