Why Does Autism Seem More Common Now?

Autism seems more common now largely because we have become better at recognising it. Diagnostic criteria have broadened, awareness has improved and people who might once have been misunderstood, given a different label or left to struggle alone are more likely to be assessed. That does not mean every question about prevalence is settled, but the rise in recorded diagnoses is not evidence that autism has suddenly appeared.

The left-handedness comparison

Left-handedness offers a useful comparison. For generations, left-handed children were discouraged, punished or forced to write with their right hand. As those practices declined, the proportion of people openly recorded as left-handed rose, particularly among younger generations. This generational difference is reflected in research on forced switching.

The number of naturally left-handed people had not suddenly changed. What changed was whether they were allowed to use their left hand and whether society recorded them accurately.

Autism is not exactly the same, but the comparison helps. When a difference is punished, hidden or poorly understood, fewer people are visibly identified with it. Once knowledge improves and stigma begins to ease, the recorded number rises. That increase can reflect visibility rather than an equally dramatic biological change.

We recognise a wider range of autistic people

Earlier ideas about autism were based on a much narrower group of people, often children with very visible support needs. Many autistic adults, autistic women and girls, and people who relied on autistic masking did not match that limited picture.

Greater understanding means professionals are now more likely to recognise different presentations of autism. People may also recognise traits in themselves after seeing a child, sibling or parent assessed. A large global prevalence review identified changes in definitions, study methods and the context in which autism is identified as important reasons prevalence estimates have risen and varied.

Some people who would now receive an autism diagnosis may previously have been described as difficult, shy, obsessive, badly behaved, oversensitive or simply odd. Others were diagnosed with a different condition without anyone noticing the autism underneath.

Autism often runs in families

Autism has a substantial genetic component, so it is not unusual for several people in one family to be autistic. Research has found a much higher likelihood of autism among younger siblings of autistic children than in the wider population. A large 2024 sibling study found that 20.2% of younger siblings in the research group were also diagnosed as autistic.

In my own family, one of my parents was strongly suspected of being autistic, but because of the attitudes and expectations they grew up with, they were never assessed. My two brothers and I are all autistic. As our family grew, the number of autistic or probably autistic people in our immediate family effectively went from one to four.

That is a genuine increase within one family, but it does not mean autism is spreading. It shows how autism can occur across generations and among several siblings. In previous generations, relatives with similar traits may never have been recognised. Genetics helps explain the family pattern; improved awareness helps explain why we can now see it.

Getting diagnosed is not easy

More diagnoses do not mean that autism assessments are casual or easy to obtain.

I waited four years on an NHS waiting list. When the assessment finally happened, it involved three straight hours of detailed and deeply personal questions. It was not a quick checklist or a case of saying, “I think I might be autistic,” and immediately receiving a diagnosis. I have written more about the experience in my late-diagnosis story.

The NHS assessment guidance explains that an adult assessment may involve questionnaires, questions about early life and present-day behaviour, medical reports, school or workplace documents and conversations with people who knew the person as a child. The process can be demanding, and access varies considerably.

Greater awareness may lead more people to seek assessment, but seeking one and receiving a diagnosis are not the same thing.

More visible does not mean newly created

There may be factors affecting underlying autism prevalence that research has not fully explained, so it would be too absolute to say the true rate has never changed at all.

What we can say is that a large part of the apparent rise comes from seeing people who were previously missed. Broader knowledge, reduced stigma, improved diagnostic practice and greater recognition of family patterns all bring autistic people into view.

The left-handed population did not suddenly appear when schools stopped forcing children to switch hands. Autistic people have not suddenly appeared either. More of us now have the language, opportunity and evidence needed to be recognised.