Cracking the Genetic Code: Why Some People Develop Autism and Others Don’t

Why Some People Develop Autism and Others Don’t

Keywords: genetic causes of autism, autism spectrum disorder, autism and DNA, autism in twins, neurodiversity, autism gene mutations, autism diagnosis, autism research 2025

Introduction: The Genetic Puzzle Behind Autism

For decades, scientists have been unraveling the complex mystery behind autism. Once wrongly attributed to parenting styles, autism spectrum disorder (ASD) is now widely recognized as a neurodevelopmental condition with deep genetic roots. But while it's clear that genes play a crucial role, the specific mechanisms are only just coming into focus.

Recent studies are uncovering how combinations of gene mutations—some inherited, some spontaneous—shape the way the brain develops. And while this progress offers hope for better understanding and support, it also raises ethical and philosophical questions about identity, diversity, and the future of genetic intervention.

From Misconceptions to Science: The Genetic Awakening

Until the late 20th century, autism was misunderstood and often stigmatized. The now-debunked "refrigerator mother" theory proposed by Leo Kanner in the 1940s blamed emotionally distant mothers for causing autism. It wasn’t until a 1977 twin study revealed that identical twins often both have autism that genetics emerged as a central factor in ASD.

This was a watershed moment. Research has since shown that if one identical twin is autistic, there's a more than 90% chance the other is too. Among fraternal twins, this drops to around 34%. These numbers far exceed the general population autism rate, which hovers around 2.8%.

Pinpointing the Genetic Variants Behind Autism

Genetic variation between humans is minimal—just 0.1%—but even tiny changes can have huge effects. In up to 20% of autism cases, scientists have identified “high-impact” mutations in single genes that significantly disrupt brain development.

One of the pioneers in this field, Professor Thomas Bourgeron, discovered mutations in genes linked to synapse formation—the connections between brain cells. Mutations in the Shank3 gene, for example, are rare but often associated with profound autism and related developmental delays.

Some mutations occur spontaneously in the embryo (de novo mutations), while others are inherited. But even when passed down, these gene variants may only cause autism when combined with other small-effect genetic differences, revealing the complex, additive nature of autism genetics.

Why One Twin Has Autism and the Other Doesn’t

Even among identical twins, where genes are nearly the same, one can be autistic and the other not. This gap highlights the influence of non-genetic, environmental factors, such as:

• Prenatal exposure to air pollution or pesticides

• Premature birth or complications during delivery

• Oxygen deprivation during childbirth

Unfortunately, in recent years, unfounded claims have re-emerged, such as the discredited vaccine-autism link. Alarmingly, vaccine-skeptic figures have been hired for new government research initiatives, prompting concern from health experts.

How the Brain Develops Differently in Autism

The most critical changes in brain development linked to autism likely occur in the second trimester of pregnancy, when the fetal cortex—the brain’s control center for memory, thinking, and problem-solving—is forming.

Genetic mutations may alter this development, sending the brain down a different pathway. This can lead to lifelong effects on communication, behavior, and learning ability.

In response, support groups have formed for families affected by known gene mutations—such as those involving the SCN2A gene—giving parents clearer expectations and connecting them with resources.

The Ethical Divide: Genetics, Identity, and the Future

While genetic research promises better diagnosis and even future therapies, it has also sparked controversy.

Some members of the autistic community fear that prenatal genetic testing could lead to selective abortions, similar to practices already used for Down syndrome in countries like Iceland. The idea of eliminating autism through genetic screening raises serious ethical concerns.

"Autism isn't something to be 'cured'," says Professor Sue Fletcher-Watson. "It’s a way of experiencing the world. Trying to erase it sends the wrong message."

Autism: Disorder or Neurodiversity?

Autism exists on a wide spectrum—from those who need 24/7 care to high-functioning individuals who consider their neurodivergence a strength. Some researchers argue for personalized treatments, while others emphasize embracing neurodiversity and providing accommodations rather than interventions.

Despite differing views, scientists continue exploring the genetics of autism. With tools like the “Reading the Mind in the Eyes” test, researchers are correlating subtle social traits with specific gene variants across tens of thousands of people. These studies reveal that genes linked to autism may also contribute to creativity, pattern recognition, and even higher intelligence—traits that have helped humans evolve.

Toward Targeted Genetic Therapies

While autism itself may not be something to “treat,” related disabilities like epilepsy, OCD, or speech delays could benefit from emerging gene therapies.

Recent clinical trials using CRISPR gene editing and lithium treatments are attempting to boost the function of unaffected gene copies to compensate for mutations. For example, Jaguar Gene Therapy has been approved to begin a trial for autistic children with Shank3 mutations and Phelan-McDermid syndrome.

These interventions are highly targeted and rely on precise genetic diagnoses, underscoring the value of understanding an individual’s unique genome.

Conclusion: Embracing Complexity and Diversity

Autism isn't caused by a single gene, nor is it simply a disorder. It's a complex, multifaceted spectrum influenced by a tapestry of genetic and environmental factors.

As researchers continue to map the human genome’s role in autism, the ultimate goal must be twofold:

1. Support those who need help—especially those with profound autism or co-occurring disabilities.

2. Celebrate and accommodate neurodiversity, ensuring that every person—regardless of how their brain works—can thrive in a society that values differences.

The future of autism research is not about “fixing” people, but about understanding, empowering, and supporting them. That’s a future worth striving for.