Post 5: What does (and doesn't) cause autism?

Welcome to week 5.  

This week's blog will look at the causes of autism.  Actually, it will look more at what doesn't cause autism, as according to NHS Choices 

"the exact cause of autism spectrum disorder is unknown"

OK, so lets look at the theories that have emerged over the 80 years since the term autism was first introduced, and rule some of them out...  an excellent place to start is by watching the TED talk by Steve Silberman 'The forgotten history of autism'.

Refrigerator mothers

One of the first myths about the cause of autism was the 'refrigerator mother' which was introduced by Bettelheim in the 1950's.  He was a child development specialist in the America who believed that the mothers were to blame.  He said that autism developed because thy were cold, distant and unable to show affection therefore the child was unable to bond.  Obviously, his theory had a negative effect on the mothers who were already struggling to support their child, and were then made to feel that they were to blame. Unfortunately as there was no other bio-medical explanation at the time the theory was supported by other health practitioners until the mid-1960s when it was challenged by Rimmer, the father of an autistic child and a psychologist.  Even today there are still some who believe that autism is a result of poor parenting, particularly in South Korea and some areas of Europe.


The MMR vaccine

Back in 1998 an article was published in a world-renowned journal 'The Lancet'.  The article gave the results of a study by Dr. Andrew Wakefield that claimed that autism symptoms appeared in 8 children within 1 month of having the Measles, Mups & Rubella (MMR) vaccine.  These claims were reported in the media and resulted in parents choosing not to let their children have the jab.  The number of 2-year olds who were vaccinated fell from 92% in 1995 to 79% in 2003, and in 2013 for the first time in 10 years there were serious outbreaks of measles in the UK.  Following the release of the article a number of large-scale studies were carried out which proved there was no link.  The original research was discredited in 2010 and Dr Wakefield was struck off the medical register, yet there are still people who believe that the MMR vaccine is to blame.

Mercury in vaccines

Another theory is that its the mercury in vaccines that cause autism.  Those who advocate this theory claim that while most people are able to secrete the mercury we come into contact with, some children aren't able to do this and the mercury ends up in their blood stream and is carried into their brain causing autism.  They believe that the levels of mercury found in the hair of people on the autism spectrum is much less than is found in neurotypical people.  This is another theory that has been discredited.

Leaky gut theory

Have a look at this article in the National Geographic magazine Autism's gut-brain connection which suggests that gut bacteria is different in people who are on the autism spectrum.  Scientific studies do not, however, validate these claims.

Genetic factors
Research has proven that autism runs in families, with studies showing that if there is one child in the family on the autism spectrum then the likelihood of having another child with AS is about 5-10%.  There have also been a number of studies looking at twins that show in identical twins there is a 60-90% chance if one twin has autism that the other will too.  In non-identical twins this number drops to 5-10%.  It doesn't mean that one or both parents themselves are on the autism spectrum, but that both parents are carrying the autism 'risk' genes and may show echoes of autism, for example, being an introvert, mildly obsessive etc.

There is currently no prenatal screening test for autism, and while a blood test may soon become a possibility there are many ethical implications against this (have a look at the article in the Guardian newspaper below 'Are we ready for a prenatal screening test in autism?').  With the introduction of a screening test for Down's Syndrome with 99% accuracy in Denmark abortion rates rose to 98% in pregnancies where Down's Syndrome was detected.  More on this in the BBC article below 'A world without Down's Syndrome?'

Environmental factors

For those who are genetically 'at risk' of having autism research has shown that certain environmental factors can increase (or reduce) the risk.  For example, one study in Norway claimed that taking folic acid before conception and during pregnancy can decrease the risk, however, another study in Denmark found no link between the two.  Studies have claimed (and disclaimed) that the following factors all increase chances of having a child on the autism spectrum:

• Depression & use of anti-depressants
• Premature birth
• Birth by ceasaran
• Older parent (either parent)
• Parents who are overweight
• Pregnancies spaced less than 1 year apart
• Exposure to chemicals, pollutants or pesticides.

So, what does cause autism?

Many in the field believe that autism is caused by a combination of genetics and the environment.  NHS Choices states:

"It's a complex condition and may occur as a result of genetic predisposition (a natural tendency), environment or unknown factors"

Further reading:

Cox, D. (2014) Are we ready for a prenatal screening test in autism? Available at: https://www.theguardian.com/science/blog/2014/may/01/prenatal-scrrening-test-autism-ethical-implications (Accessed: 6 August 2017).

Gee, A. (2016) A world without Down's Syndrome?' Available at: http://www.bbc.co.uk/news/magazine-37500189 (Accessed: 6 August 2017)

Contact:

If you have any queries or concerns over the Summer you can contact me directly at lesley.english@cumbria.ac.uk 

For general queries relating to the peer mentoring scheme contact peermentoring@cumbria.ac.uk 

I look forward to meeting you all in September.