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What Causes Autism? New Research Unlocks More Secrets

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What Causes Autism? New Research Unlocks More Secrets

A number of disorders exist on the autism spectrum (ASD). These include autism, pervasive developmental disorder not otherwise specified, and Asperger syndrome. ASD holds its secrets closely, but researchers are working hard to understand its causes and find ways to improve the lives of those who have the disorder, and the families who love them.

People with ASD have a different way of learning, paying attention or reacting to things. The ability to learn, think and problem solve varies greatly in people with ASD, from gifted to severely challenged. They also show differences in the way they relate to people and the way they communicate or deal with emotion. The severity and combination of symptoms can vary vastly from person to person, but the symptoms are likely to include:

  • a resistance to change,
  • difficulty adapting to changes in routine,
  • repetitive actions,
  • repetitive play,
  • repetition of words or phrases,
  • little or no interest in other people or objects,
  • may show interest in people but not able to relate to them,
  • difficulty understanding other people’s feelings and expressing their own,
  • avoids or resists being cuddled or seem to ignore people when spoken to, but responsive to other sounds,
  • difficulty expressing what they want,
  • unusual reactions to the way things look, sound, smell, taste or feel,
  • obsessive interests,
  • prefers to ply alone,
  • difficult to comfort during distress,
  • reverses pronouns (‘you’ instead of ‘I’),
  • does not play pretend games.

What Causes Autism?

We don’t know exactly what causes ASD. Up to now, differences in brain development have been thought to be the cause. New research, published in the journal Cell, has found that there seems to be more to it than that. 

A study in mice has found that some symptoms of ASD, such as touch perception, anxiety and social difficulties, are caused by problems with the nerve cells that send sensory information (such as information about touch) to the brain. They are the nerves that are found in the arms and legs, fingers and toes, and other parts of the body. (Researchers often use mice in their studies because of genetic and biological similarities between mice and humans.)

It is as though the volume of these nerve cells is turned up, so the sensation of touch is exaggerated and intense. This seems to lead to anxiety and the behavioural problems that are often associated with ASD.

“An underlying assumption has been that ASD is solely a disease of the brain, but we’ve found that may not always be the case.” David Ginty, Professor of Neurobiology at Harvard Medical School.

The Research. What they did.

Though the exact cause of ASD is unknown, there does seem to be a genetic basis. Exactly how this genetic vulnerability leads to the development of ASD is unclear, and this is where the work lies for researchers. Is there a specific combination of genes? Do the gene mutations interact with something in the environment? So many questions, but researchers are getting closer to uncovering more of the secrets of ASD.

As part of the study, researchers looked at a number of genes mutations that are known to be associated with ASD in humans.  They genetically engineered the mice to have these mutations only in the cells of their peripheral sensory nerve cells. These are the nerve cells in the extremities of the body – arms, legs, fingers toes.

They also looked at two other genes that have been associated with behaviours that are typical of ASD. These genes are crucial for nerve cells to function normally, and previous research has connected the mutations to problems with the way nerve cells communicate with each other. 

(For the scientific ones out there, researchers were looking at mutations in the Mecp2, Gabrb3, Shank3, and Fmr1 genes.)

“Although we know about several genes associated with ASD, a challenge and a major goal has been to find where in the nervous system the problems occur … By engineering mice that have these mutations only in their peripheral sensory neurons, which detect light touch stimuli acting on the skin, we’ve shown that mutations there are both necessary and sufficient for creating mice with an abnormal hypersensitivity to touch.” David Ginty.

Sensitivity to touch.

The researchers looked at how the mice reacted when they were touched gently. In the study, the touch was from a gentle puff of air on their backs. The study also explored whether the mice could tell the difference between objects that had different textures.

The mice that were bred to have the ASD gene mutation in only their sensory nerve cells showed:

  • a heightened sensitivity to touch;
  • an inability to tell the difference between textures;
  • an abnormality in the transmission of impulses between the nerves in the skin and spinal cord – these are the nerves that send touch signals to the brain.
Anxiety and Social Interactions

The researchers then turned their attention to anxiety and the way the mice interacted socially. They looked at how much the mice avoided being out in the open and how they interacted with unfamiliar mice.

The mice that were bred to have the ASD gene mutations showed heightened levels of anxiety. They also interacted less with the mice they hadn’t seen before.

‘A key aspect of this work is that we’ve shown that a tactile, somatosensory dysfunction contributes to behavioral deficits, something that hasn’t been seen before … In this case, that deficit is anxiety and problems with social interactions.’ David Ginty.

The research has revealed the ‘what’, but the ‘how’ is still vague. What we know is that the mutations in the sensory nerve cells cause problems for the way the body interprets touch. This seems to contribute to anxiety and social problems, but exactly how it contributes isn’t yet clear. 

‘Based on our findings, we think mice with these ASD-associated gene mutations have a major defect in the ‘volume switch’ in their peripheral sensory neurons,’ Dr Lauren Orefice, researcher.

Because the volume of these nerve cells seems to be turned all the way up, the sensation of touch is strong and severe. 

‘The sense of touch is important for mediating our interactions with the environment, and for how we navigate the world around us … An abnormal sense of touch is only one aspect of ASD, and while we don’t claim this explains all the pathologies seen in people, defects in touch processing may help to explain some of the behaviors observed in patients with ASD.’ Dr Lauren Orefice.

Where to from here.

With every new piece of research, we move closer to finding a cure. Researchers are now looking into treatments that might turn down the ‘volume’ in the peripheral sensory neurons to levels that are more manageable. They are looking into both genetic and pharmaceutical possibilities.

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10 Comments

Kristy Thorburn

The term ‘ASD’ is now considered offensive by many Autistic people. My understanding is that neurodivergence is no longer something considered to be ‘disordered’ – just different.

Reply
Hey Sigmund

Kristy, Austism Spectrum Disorder (‘ASD’) is the official clinical term used to refer to all conditions that lie on the autism spectrum, of which autism is one. It is the term set down by the American Psychiatric Association in the DSM-5 (the fifth edition of the Diagnostic and Statistical Manual) which is the official manual used by clinicians universally for diagnosis of all conditions to do with mental health. Here is a link to a paper by the American Psychiatric Association which explains their use of ASD in the DSM-5 http://www.dsm5.org/Documents/Autism%20Spectrum%20Disorder%20Fact%20Sheet.pdf. The research paper on which this article is based uses the term ASD as this is the official clinical term for all conditions that lie in the autism spectrum, of which autism is one. The link to the research paper is in the article.

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Judy

What I need to know is how to relate to a child with autism. I have a 6-year-old grandson who is autistic and displays many of the characteristics mentioned above – ie: avoids eye contact, doesn’t respond to questions, runs back and forth flapping his arms/hands, is uncomfortable with touch/hugs. I don’t want to have unreasonable expectations of him. I find his father (my son who we now know has Aspergers syndrome) is often very stern with Connor – “Look at Nanny”, “Nanny asked you a question”, etc. What I really need is help in how to communicate and be with him, and with his father. Can you recommend a program in the Vancouver, BC area, or a book that would be of help. Personally, I don’t feel we should be trying to make him adapt so much as We need to adapt. Thank you.

Reply
Hey Sigmund

Judy there are some great organisations that can help you with this. I live in Australia, so can’t personally recommend any in Vancouver, but if you google ‘autism Vancouver’ there will be a number of them that come up. Have a look and see if there is something that feels as though it might be able to give you the support you need. It’s wonderful that you want to know how to be the best you can be for your grandson. Whatever you decide to do, it’s important that it is consistent with what his dad is doing. As with all kids, there needs to be as much consistency and clarity as possible so as not to confuse them about what to expect or the behaviours that are allowed.

Reply
Judy

Thank you so much for getting back to me, and so quickly. I really appreciate it. I particularly appreciate your advice re being consistent with what Connor’s dad is doing. That is very good reinforcement for me. And yes, I have been in touch with the Autism Society in Vancouver. However, they haven’t been very good at getting back to me. Also I live in a small community outside of Vancouver that is a ferry ride and travelling time to get to the city. If you could recommend a good book, that would be great.

Reply
Lisa

Hi Karen, This is a great article that certainly offers us hope. My 19 year old has struggled with autism since the age of 2. He is a wonderful young man who will find life much easier if a cure can be found for his anxiety and touch sensitivity. My son agrees with me that his difficulties have felt like a ‘disorder’ in that he has needed a lot of support to find his place in the world and he would struggle without help. Finding a cure, or at least alleviating his anxiety, would be so beneficial for his independence. Thank you for this information.

Reply
Hey Sigmund

Thanks Lisa. There is so much research happening around this and I feel so sure they are getting closer to finding something that will ease symptoms and make life easier for people with autism. They deserve it. Hopefully soon.

Reply
Laurel

My 8 yo grandson has ASD with accompanying anxiety. He does not exhibit the anti -touch symptoms and is very loving. He is brilliant and gets bored easily with the classroom schedule and level of topics . He has difficulty playing with and relating to other children. The most difficult situations occur when he gets upset over a seemingly insignificant
Issue ( to others) and remains in the upset loop.
My heart aches for him and the family, as we are all
Affected by this divergence.
Thank you for the article. I look forward to future
Reports
Laurel

Reply
Hey Sigmund

You’re so welcome Laurel. Your grandson sounds like a gorgeous young man with so much to offer the world. Hopefully we are getting closer to understanding more about ASD. I will keep writing about new research here.

Reply

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