A new study published in Nature is turning longstanding assumptions about autism on their head. For years, those diagnosed with autism spectrum disorder after the age of six—the current median age of diagnosis—were often thought to have a “milder” form of the condition.

However, recent genetic analysis reveals a far more complex picture. Rather than being simply less severe, autism diagnosed later in childhood or adolescence appears to be fundamentally different at the genetic level.

Researchers from leading institutions, including the University of Cambridge, have found that the genetic profiles of individuals diagnosed later in life bear little resemblance to those diagnosed as toddlers.

The late-diagnosis group’s genetic make-up is more similar to those with depression, attention-deficit/hyperactivity disorder (ADHD), and post-traumatic stress disorder (PTSD) than to early-diagnosed autism.

This finding underscores what experts have been saying for years: autism is not a single disorder with a singular cause. Instead, it is an umbrella term for a collection of related but distinct neuro-developmental conditions.

Genetic data played a central role in this study. Researchers did not zero in on a few specific genes. Instead, they analysed thousands of genetic variants influencing traits such as social interaction and emotional regulation.

It turns out that while some genetic patterns predispose children to social difficulties from an early age, other genetic combinations may result in challenges that only become apparent later in childhood or adolescence.

This delay in the emergence of symptoms can result in missed opportunities for early support. Many children whose symptoms do not fit the classic early-childhood profile fall through the cracks until problems intensify.

Experts point out that these children may not receive a diagnosis until they are struggling significantly, by which point they may already be experiencing emotional distress and social isolation.

The study reviewed long-term behavioural and genetic data from more than 45,000 people across Europe, the United Kingdom, Australia, and the United States. The results painted a nuanced picture of autism’s genetic landscape.

Adolescents diagnosed with autism faced pronounced difficulties with emotional regulation and peer relationships. These challenges were often compounded by undiagnosed depression or anxiety.

Late diagnosis is particularly common among women. Data indicates that a quarter of women with autism receive their diagnosis at 19 or older, compared to just 12 percent of men. Reasons for this disparity are complex but likely involve differences in how autism presents in girls and women, as well as societal expectations and diagnostic biases.

The lived experiences of those diagnosed late in life highlight the emotional toll exacted by years without understanding or support. Many recount periods of deep frustration, confusion, and isolation, sometimes leading to depression or thoughts of self-harm. The relief and clarity that comes with a diagnosis can be transformative, prompting shifts in career, relationships, and self-acceptance.

Many described excelling academically yet feeling fundamentally lost in social situations. Simple classroom lessons were straightforward, but unwritten social rules remained inscrutable.

When a diagnosis finally arrived in adulthood, it provided a long-sought explanation for years of struggle. This newfound understanding led to changes in career direction and ultimately to a rewarding role supporting others with similar experiences.

Experts emphasise that timely diagnosis is crucial for providing critical support. Over the last decade, increased awareness and improved access to assessment have driven down the average age at which children are diagnosed with autism. Yet many still slip through the net due to limited resources or less typical presentations.

Meanwhile, growing acceptance of neurodiversity has encouraged more teenagers and adults to pursue assessment. The Nature study marks the first time researchers have linked genetic profiles to the timing of an autism diagnosis.

Notably, those receiving later diagnoses showed an elevated risk for depression—likely the result of both genetic predisposition and years without appropriate support. Social exclusion, bullying, and lack of understanding all take their toll on young people who struggle without knowing why.

The importance of environment cannot be overstated. Researchers suggest that future studies should examine how supportive or hostile settings influence mental health outcomes for those diagnosed later in life. Services often focus on children, but experts argue that support must be extended across the lifespan.

The pressure to “blend in” exacts a significant emotional cost. Accounts from adults diagnosed late in life describe childhoods marked by relentless efforts to mask their differences—sometimes at great psychological expense. Coping mechanisms such as repetitive behaviours might provide comfort but can also make children targets for bullying or ridicule.

The effort to suppress natural behaviours can lead to anxiety and panic attacks. Without a framework for understanding their differences, many spend years feeling lost or out of step with their peers. Only with diagnosis does the pattern become clear, allowing individuals to redirect their energy toward personal growth and well-being instead of constant self-correction.

Interestingly, for some, receiving an autism diagnosis in adulthood has been a profoundly positive turning point. It enables greater self-acceptance and empowers individuals to seek out environments and relationships that suit their unique needs. Some even use their experiences to inform research or advocacy work, helping others who are following similar paths.

Experts stress that while understanding the causes of autism is important, research must also focus on improving quality of life for those living with the condition. Many autistic individuals possess remarkable strengths and bring joy both to themselves and those around them—sometimes finding delight in activities others might overlook.

Autism’s complexity defies easy explanations or one-size-fits-all solutions. The new findings add further weight to calls for nuanced approaches in both diagnosis and support. Autism is shaped by a diverse tapestry of genetic factors interacting with individual development and environment over time.

Contrary to popular belief, there is no single cause or universal presentation. Claims linking autism to specific environmental factors or medications have repeatedly failed to withstand scientific scrutiny; genetics play a central role not only in who develops autism but also in how it manifests.

The message from this new research is clear: autism must be understood as a spectrum not just in terms of severity but also in terms of underlying biology and timing of onset.

Personalised approaches are essential—from assessment through support services—to accommodate the full diversity within the autistic community.

Support systems must evolve accordingly. As awareness grows and diagnosis rates rise across all age groups, there is both an opportunity and an obligation to ensure services are available for people of all ages—whether they receive their diagnosis as children, teenagers or adults.

For anyone struggling with feelings of isolation or distress—whether related to autism or not—help is available through national helplines and online resources dedicated to mental health support.

The landscape of autism is changing rapidly as science sheds new light on its origins and manifestations. Continued research promises not only greater understanding but also real hope for more effective support strategies tailored to every stage of life.