Autism & Genetics: Understanding a Complex Spectrum Without Reducing Individuals

Autism is as fascinating as it is misunderstood. For some, a Christmas party might feel like an overwhelming storm of lights and sound. For others, their inner world is shaped by remarkable creativity, musical talent, or an exceptional eye for detail.

This contrast captures what autism represents today: a broad spectrum, marked by diverse manifestations and widely varying needs.

Beyond misconceptions, genetic science now offers deeper insight into the neurodevelopmental differences that shape this spectrum — without ever reducing autism to a single explanation.

1. Autism: A Spectrum, Not a Single Category

The rise in autism diagnoses over recent decades has sometimes been interpreted as an “epidemic.” Yet much of this increase reflects:

• a much broader diagnostic definition;
• greater awareness;
• more precise and earlier screening tools.

Today, autism encompasses highly diverse profiles — from individuals requiring intensive daily support to adults who are fully autonomous yet struggle with social communication or sensory regulation.

This diversity is real — and genetics is beginning to shed light on why.

2. A Strong Genetic Foundation… but Not the Whole Story

Studies consistently show that autism is highly heritable (over 80%).
This does not mean there is a single “autism gene,” nor that genetics alone explain everything. Rather, it suggests that the biological differences underlying the spectrum are largely genetic in origin, while still interacting with many other factors.

✔️ Rare “high-impact” genetic variants

In some children, a single mutation or duplication can cause significant developmental challenges. These variants often affect genes involved in neural communication, such as SHANK3 or NLGN3.

They account for roughly 20% of diagnoses, and are often associated with other conditions such as epilepsy or intellectual disability.

✔️ Common variants, widespread in the population

More often, autism results from the accumulation of hundreds of subtle genetic variations, each one slightly increasing risk.

Two parents who carry several autism-linked variants — even without a diagnosis themselves — may pass them on, and it is the combination that determines whether a child meets diagnostic criteria.

✔️ Brain regions involved

Many common variants cluster in genes active in brain regions linked to:

• social perception (amygdala),
• memory (hippocampus),
• sensory integration (neocortex).

These findings reinforce the idea that autism arises from multiple neurodevelopmental pathways, rather than a single biological cause.

3. What if Autism Isn’t One Condition, but Several?

Recent research examining the developmental and genetic profiles of thousands of autistic children has identified four biologically distinct subgroups, each with its own behavioural and genetic characteristics:

• a “highly affected” group, often carrying rare mutations;
• a “moderate” group with fewer limitations;
• a “mixed” group combining developmental delays and limited anxiety;
• a “social/behavioural” group, often diagnosed later and frequently associated with anxiety, ADHD, or depression.

These categories are not meant to add labels, but to better understand real needs.

This work points to very different developmental trajectories hidden beneath a shared administrative diagnosis — and opens the door to:

• more personalized support,
• better anticipation of comorbidities,
• clearer understanding of each individual’s functioning.

4. Environment: A Real but Subtle Influence

Discussing environmental influences in autism requires care. Some ideas have been distorted by harmful myths — most notably the discredited claim linking vaccines to autism.

Current scientific evidence is unequivocal:
no causal link has ever been found between vaccination and autism.

However, other environmental factors warrant attention:

• advanced parental age, which increases the likelihood of new germline mutations;
• certain medications during pregnancy (e.g., valproate);
• significant exposure to air pollution;
• severe maternal infections with high fever, according to observational studies.

These are risk factors, not deterministic causes — and they almost always interact with underlying genetic predispositions.

5. Toward a More Nuanced — and More Human — Understanding of Autism

The purpose of genetics is not to classify people, but to help understand mechanisms that can guide support, such as:

• earlier screening,
• individualized adaptation strategies,
• identification of comorbidities (e.g., anxiety, ADHD),
• future development of targeted therapies,
• improved educational and social policies.

Science supports what autistic communities have long expressed:
autism is not homogeneous, and there is no single way to be autistic.

6. Adnà’s Position: More Learning, Less Judging

At Adnà, we approach these questions with humility and respect.

We recognize that, for many families, autism is a demanding and often exhausting reality, requiring significant emotional, financial, and human resources.

We also know that many autistic individuals carry a history of misunderstanding, silent struggle, but also unique strengths and valuable perspectives.

Our conviction is not that “everything is positive,” nor that autism is simply “another difference.”
Our conviction is that:

• understanding genetic and environmental mechanisms helps us better understand people,
• this knowledge should help us adapt schools, services, environments, and public policies,
• and support families living with a condition that can be very heavy, without blame or false promises of a “miracle solution.”

Our role is not to tell families what to think, but to offer reliable, nuanced, science-based information, so they can move forward with more clarity in what is often a complex journey.

Because behind every diagnosis, there is a person, a family, a story — and genetics is only one tool to help us understand them, never to reduce them.