Autism Research Indirectly Identifies Flu Vaccines as a Cause

tress can send your stomach into a painful tailspin, causing cramps, spasms and grumbling. But trouble in the gut can also affect the brain.

This two-way relationship may be an unlikely key to solving one of medicine’s most pressing — and perplexing — mysteries: autism. Nearly 60 years after the disorder was first identified, the number of cases has surged, and the United Nations estimates that up to 70 million people worldwide fall on the autism spectrum. Yet there is no known cause or cure.

Autism is a complex spectrum of disorders that share three classic features — impaired communication, poor social engagement and repetitive behaviors. On one end of the spectrum are people who are socially awkward but, in many cases, incredibly bright. At the other extreme are individuals with severe mental disabilities and behavioral problems.

Treatment for autism may one day come in the form of a probiotic — live, ’friendly’ bacteria like those found in yogurt.

Among autistic children’s most common health complaints? Gastrointestinal problems. Although estimates vary widely, some studies have concluded that up to 90 percent of autistic children suffer from tummy troubles. According to the CDC, they’re more than 3.5 times more likely to experience chronic diarrhea and constipation than their normally developing peers.

Following these hints, Arizona State University researchers analyzed the gut bacteria in fecal samples obtained from autistic and normally developing children. They found that autistic participants had many fewer types of bacteria, probably making the gut more susceptible to attack from disease-causing pathogens. Other studies have also found striking differences in the types and abundance of gut bacteria in autistic versus healthy patients.

But is the gut microbiome in autistic individuals responsible for the disorder? To find out, Caltech postdoctoral researcher Elaine Hsiao engineered mice based on earlier studies showing that women who get the flu during pregnancy double their risk of giving birth to an autistic child. In the mouse model, pregnant females injected with a mock virus gave birth to pups with autism-like symptoms, such as obsessive grooming, anxiety and aloofness.

The mouse pups went on to develop so-called “leaky gut,” in which molecules produced by the gut bacteria trickle into the bloodstream, possibly reaching the brain — a condition also seen in autistic children.

But how did these bacteria influence behavior? To find out, Hsiao analyzed the mice’s blood. The blood of “autistic” mice contained a whopping 46 times more 4EPS, a molecule produced by gut bacteria, thought to have seeped from their intestines. What’s more, injecting healthy mice with 4EPS made them more anxious. A similar molecule has been detected at elevated levels in autistic patients.

Read more: Autism’s Gut-Brain Connection | Fast forward | OZY

“women who get the flu during pregnancy double their risk of giving birth to an autistic child. In the mouse model, pregnant females injected with a mock virus gave birth to pups with autism-like symptoms, such as obsessive grooming, anxiety and aloofness.”

How is this not a link between flu vaccines and autism?

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