Autism is a complex neurological condition affecting social interaction, communication, learning, and behavior. Though it can be diagnosed at any age, signs usually appear within the first two years of life.
Understanding Autism and Its Causes
Research shows autism has a genetic basis—if one identical twin has autism, the other is more likely to have it. These genes influence how brain cells connect. However, genes explain only about half the risk.
Other factors play a role alongside genetics. For example, if a mother catches an infection like measles during pregnancy, the child’s risk of autism rises. Maternal health problems such as obesity and diabetes also increase the chance.
Recent studies highlight a surprising factor: the gut-brain connection. Autism is a spectrum disorder, meaning there are many types, each possibly caused by different factors. Poet Karla Culbertson likens autism to a fingerprint—no two cases are exactly the same.
Controversy Over Vaccines
Robert F. Kennedy, the new U.S. Secretary of Health and Human Services, controversially believes vaccines cause autism, echoing discredited claims by Andrew Wakefield. Wakefield’s medical license was revoked for misconduct related to anti-vaccine research. The scientific consensus, based on decades of studies, firmly rejects any link between vaccines and autism. Ironically, vaccine skepticism has led to more measles cases, which can increase autism risk.
The Microbial Fingerprint of Autism
Scientists have discovered unique patterns of microbes in the mouths and guts of autistic individuals. Kathy Kar-man Shum from the University of Hong Kong found that analyzing oral bacteria can predict autism with 80% accuracy. This simple test during a dental check-up could lead to early detection and intervention, when treatment is most effective.
Immune System and Inflammation
Some autistic children show fewer symptoms when they have a fever. Research with autistic mice links this to cytokines—immune molecules that signal inflammation. One cytokine, IL-17, acts both as an immune signal and a neurotransmitter in the brain.
In mice whose autism-like symptoms come from maternal illness, IL-17 affects a small brain area involved in social behavior. When IL-17 is triggered by pieces of bacteria introduced into the gut, these mice act more socially and less repetitively.
While this does not mean fevers can treat autism, it shows the immune system and inflammation play a role in autistic behavior.
The Gut Microbiome’s Role
John Cryan and Ted Dinan at University College Cork have identified gut bacteria linked to autism in mice. They also found microbes like Blautia stercoris that reduce symptoms. Cryan explains that the social brain is especially sensitive to signals from the gut microbiome.
In humans, autistic children tend to have fewer gut bacteria such as Veillonella, Coprococcus, and Prevotella. These bacteria help produce neurotransmitters like GABA and serotonin, which can calm agitation.
A study at USC and UCLA led by Emeran Mayer found autistic children have lower levels of tryptophan, a building block for serotonin, in their guts. This links to changes in brain activity and greater autism severity.
From Correlation to Cause
Cal Tech researcher Sarkis Mazmanian transferred stool samples from autistic and non-autistic humans into mice. Mice receiving samples from autistic donors showed autism-like behaviors, while controls did not. This is strong evidence that gut microbes can influence behavior.
Many autistic children have unique eating habits, which may reinforce their abnormal gut bacteria. Probiotics and prebiotics could help. A study from Arizona State University showed probiotic treatment reduced stomach problems and improved autism symptoms by nearly 50%.
Looking Ahead
Autism remains a puzzle, but growing evidence links the brain and gut in important ways. Continued research could lead to new treatments targeting gut microbes to improve the lives of autistic individuals.
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