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Biological Explanations for Autism

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Biological Explanations for Autism

Many different psychologists are still studying the causes of autism, and one particularly prominent theory is that of a biological basis of autism. First and foremost, they ask if there is a biological basis of autism. Are there genetic causes of autism? Or is it a result of the environment? Perhaps it’s a combination of both.

What are the characteristics of autism?

For years, it has been questioned as to what causes autism. Ultimately, this is still not known. Researchers have explored potential biological, environmental, genetic and psychological factors of autism.

Autism, also referred to as Autism Spectrum Disorder (ASD), is a developmental disorder that often impacts social, emotional and communication skills.

ASD may cause a person to perform repetitive behaviours, be highly revolved around routine and have difficulties with attention. A person with autism may have difficulties learning and can suffer from feeling overwhelmed for various reasons, including sensitivity to sensory experiences (e.g. loud noises).

Some psychologists see a possible link between biological and environmental causes of autism. For example, they believe that both genetic factors and environmental factors, such as lack of play, can lead to autism. Overall, however, it is not yet clear whether autism is biological or environmental.

Biological Explanations for Autism Play therapy StudySmarterPlay therapy, Pixabay

Biological basis of autism

Autism is considered to have a biological basis. We will also touch upon the infamous vaccine debate. Biological explanations for your exam to consider are:

  1. The amygdala

  2. Vitamin A

  3. Twin studies

  4. Fragile X gene

  5. Rett syndrome

The amygdala and autism

Baron-Cohen et al. (2000) consider the biological approach to autism by focusing on the amygdala’s role linked to social intelligence. They theorised that abnormalities with the amygdala might be associated with autism. They assessed autistic people using functional magnetic resonance imaging (fMRI) when they were judging the expression of other people’s eyes (infer one’s feelings from photos of eyes). They had to think about what the other person was thinking/feeling.

Baron-Cohen et al. (2000) found that patients with autism did not activate the amygdala when attempting to understand or make mental judgements on the emotions in other people’s eyes. In contrast, the controls (people without autism) showed amygdala activity. This evidence suggests impairment of the amygdala is essential for explaining why those with autism lack social abilities, empathy, and the ability to make eye contact.

Bioloigcal Explanations for Autism Baron-Cohen et al. (2000) study on amygdala lack of eye contact StudySmarterPeople with autism often lack the ability to make eye contact, Flaticon

Vitamin A and autism

A lack of vitamin A impacting retinoid receptors in the brain is thought to cause symptoms of autism, such as lack of socialisation, eye contact, and sleep disruption. Megson (2000) supported this hypothesis by providing many children with autism vitamin A for two months. Abilities to socialise, language use, and eye contact significantly improved after taking vitamin A for two months.

One explanation explores the possibility that a lack of vitamin A during pregnancy can impact the development of the foetus in the womb, impacting abilities such as socialising, language use, and eye contact (Liu et al., 2021).

Genetic causes of autism

Genes may also be a cause of autism, or they may contribute to the development of the disorder.

Twin studies and autism

Rodier (2000) focused on genetic factors that contribute to autism. Rodier found in MZ twins (who share 100% of their DNA) that if one twin had autism, there was a 90% chance that the other twin would develop the disorder.

The fragile X gene and autism

Autism biological research supports the idea that genes with the fragile X syndrome contribute to the development of autism. The FMR1 gene, responsible for causing fragile X syndrome, is responsible for 26% of cases of autism, therefore highlighting a potential link between the fragile X syndrome gene, causing autism in some individuals.

Rett syndrome and autism

To support the theory of genetic causes of autism, Amir et al. (1999) found mutations in the MECP2 gene as the cause of Rett syndrome. Rett syndrome crosses over with features of autism with traits such as repetitive behaviours, regression, and motor abnormalities. It is on the autism spectrum.

This mutation in the MECP2 gene accounts for around 80% of cases of Rett syndrome. Chao (2010) conducted a study to support these results and found that mice lacking the MECP2 gene developed many behaviours similar to that of Rett’s syndrome and autistic features such as repetitive behaviours.

Rett syndrome affects girls predominantly, and a variant known as Preserved Speech Variant (PSV) is a milder version of Rett syndrome and showcases more autistic behaviours. Zappella et al. (2003) found that after studying two girls who fit into the PSV criteria, on a long follow-up on their behaviours, their initial behaviour followed the trajectory of the first few stages of Rett syndrome.

However, they lost their autistic behaviours over the years and reached an IQ of 45. As a result, we cannot conclusively say the MECP2 gene is the cause of autism, just associated with it.

Biological Explanations for Autism Genetic Causes of Autism MECP2 gene StudySmarterDNA mutations, Flaticon

MMR II vaccine and autism

During the 1990s, the prevalence of autism dramatically increased (Ratajczak, 2011). Coincidentally, this coincided with the marketing of the second version of the measles, mumps, and rubella vaccine (MMR II.) This vaccine was contaminated with human tissue from the lung. It was suggested the increase in autism was due to this vaccine (Ratajczak, 2011).

There are issues with this assumption. For example, Lievano et al. (2012) outlined that over 32 years of marketing the vaccine, there were 433 diagnoses of autism following vaccinations. Therefore, out of 575 million distributed doses, it is improbable that the MMR II vaccine is a potential cause of autism.

This theory has so far been debunked. The author of the original paper claiming the link existed, Andrew Wakefield, was discredited and struck off the UK medical council.

The prevalence of autism may also be down to better diagnostic criteria and techniques. People are far more aware of the disorder and are more likely to seek professional help. Medical doctors are also more aware of the disorder, explaining the rising diagnosis.


Biological Explanations for Autism - Key takeaways

  • The exact causes of autism are not known.

  • Biological explanations of autism include the involvement of underactive amygdala activity in the brain and vitamin A deficiency.

  • Genetic explanations of autism explore how particular genes may lead to autism, including the Rett syndrome gene, fragile X gene and MECP2 gene.

  • In the 1990s, an increase in autism was linked to the vaccine MMR II. This theory has since been disproved.

  • The prevalence of autism may be down to better diagnostic criteria and techniques.

Frequently Asked Questions about Biological Explanations for Autism

Autism is thought to have a biological basis. The role of parts of the brain, such as the amygdala, has been considered as a possible explanation for autism. In addition, the role of vitamin A and its association with autism has also been considered. Genes also play a role, as MZ twins (twins who share 100% of their DNA) have a high concordance rate in autism diagnosis.

Autism is associated with both biological and environmental explanations. Some psychologists see a possible link between biological and environmental causes of autism. For example, they believe that both genetic factors and environmental factors such as lack of play can lead to autism. Overall, however, it is not yet clear whether autism is biological or environmental.

The genetic cause of autism explores how autism can be passed down through genes. Several genes have been explored, including the Rett Syndrome gene, Fragile X gene, and MECP2 gene. Therefore, it is not known what exact genes may cause autism.

A potential biological marker for autism that has been explored in research is an underactive amygdala. An underactive amygdala has been linked to people with autism lacking social abilities, empathy, and the ability to make eye contact.

One explanation explores the possibility that a lack of vitamin A during pregnancy can impact the development of the foetus in the womb, impacting abilities such as socialising, language use, and eye contact. 

Final Biological Explanations for Autism Quiz

Question

A study found that children’s abilities to socialise, use language and maintain eye contact significantly improved after taking vitamin A for two months. True or false?

Show answer

Answer

True.

Show question

Question

Is too much or too little Vitamin A thought to be linked to autism?

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Answer

Too little. A lack of vitamin A during pregnancy can impact the development of the foetus in the womb, impacting abilities such as socialising, language use and eye contact.

Show question

Question

Systemising involves the ability and knowledge to express empathy. True or false?

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Answer

False. Systemising involves the ability and knowledge to identify rules and predict and understand how a system works.

Show question

Question

During the 1990’s, the prevalence of autism dramatically increased. True or false? 


Show answer

Answer

True.

Show question

Question

Research found that in MZ twins (who share 100% of the DNA), if one twin has autism, there is a ___% chance that the other twin will develop the disorder.

Show answer

Answer

60%

Show question

Question

MMR II vaccine is the definite cause of autism. True or false?

Show answer

Answer

False.  Lievano et al. (2012) outlined that over 32 years of marketing the vaccine, there were 433 diagnoses of autism following vaccinations. Therefore, out of 575 million distributed doses, it is improbable that the MMR II vaccine is a potential cause of autism.

Show question

Question

An underactive amygdala has been linked to explaining why those with autism lack social abilities, empathy and ability to make eye contact. True or false?

Show answer

Answer

True.

Show question

Question

Rett syndrome crosses over with features of autism, such as excellent communication skills and empathy. True or false? 

Show answer

Answer

False. Rett syndrome crosses over with features of autism, such as repetitive behaviours, regression and motor abnormalities.

Show question

Question

How much DNA do MZ twins share?

Show answer

Answer

100%

Show question

Question

Autism is a developmental disorderTrue or false?


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Answer

True. 

Show question

Question

The FXS gene, responsible for causing the fragile X syndrome, is responsible for ___% of cases of autism.

Show answer

Answer

2–6%

Show question

60%

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