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Many autistic Britons may not in fact have the disorder, a leading expert in the condition has warned - amid an alarming surge diagnoses.

The definition of the problem with learning and development has become 'too broad', 'vague' and influenced by 'misleading' ideas spread on social media, according to Professor Dame Uta Frith.

Prof Frith, from the Institute of Cognitive Neuroscience at University College London, authored pioneering research in 1960s and 70s that defined the medical establishment's understanding of autism, and its impact on daily life.

In a strongly worded paper published today, the psychologist remarked on the dramatic change in criteria for diagnosis of the disorder over the last 80 years.

'When it was first identified in the 1940s, it referred to a small group of children with severe difficulties in social interaction, communication and behaviour,' Prof Frith wrote in the journal Psychological Medicine.

'Over time, the definition has widened to include people with milder traits and no language or learning problems.

'Today, anyone of any age or intelligence level can be diagnosed with autism if they meet certain criteria.'

She added that the term has become a 'catch all diagnosis' for other psychological problems that require different treatment.

Dame Uta Frith, who pioneered much of the research that underpins autism, says the desire for inclusiveness has led to 'overinclusion'

Recent figures show the number of UK patients awaiting specialist help for autism has tripled since 2021.

More than 200,000 people are now awaiting an assesment, equivalent to the population of Luton or Portsmouth.

Over the last 20 years, meanwhile, diagnoses have surged by more than 700 per cent, according to studies.

Experts have previously blamed increased awareness of the signs of the condition, fuelled by videos posted to social media, for the increase.

Autism is a lifelong disability that influences how people experience and interact with the world.

It commonly causes problems with communicating, socialising and learning.

Some also have a learning disability, and those with the disorder are at higher risk of a range of physical and mental health conditions including epilepsy, eating disorders and anxiety.

Charities now describe autism as a 'neurodivergence', rather than developmental problem. But Prof Frith says this further fuels misunderstandings.

'While this helps reduce stigma, it also creates tension,' she wrote. 'If autism is not a disorder, why use a medical diagnosis?'

The expert blamed social media for 'spreading simplified ideas' about autism. The diagnosis, she said, has 'become part of popular culture'.

'Social media, films, and online communities have helped people share experiences, but they have also spread simplified or misleading ideas.'

Prof Frith has called for medical professionals to identify other psychological problems that may be at play, and treat patients appropriately.

'There are ways to reduce the symptoms of anxiety disorder and depression,' she said. 'There are also ways to build resilience in the face of significant social stress.' She added that these approaches would not be appropriate for autism that's diagnosed in childhood.

Meanwhile, therapies are available for problems that are known to be specific to autism, such as feelings of burnout and sensory overload.

'Such a reorientation would signpost a new route toward correct support...and counteract the tragic neglect of those with the most severe impairments,' she said.

It's estimated that around three per cent of UK children have autism.

Early signs include avoiding eye contact, not responding to their name, repetitive movements and reduced engagement in play, according to the NHS.

Reacting to the essay, Mel Merritt, head of policy and influencing at the National Autistic Society, said: 'Autism is understood as a spectrum. As the article points out, in the past people thought the spectrum was a straight line between ‘more’ and ‘less’ autistic, but this isn’t right.

'Today we understand the spectrum to mean each autistic person has a unique combination of characteristics.

'Terms such as milder traits may be misleading or unhelpful in reflecting the difficulties and impact of navigating daily life for so many. Autistic people can be very different to one another, each with a unique set of strengths and challenges. This should not take away from or ‘neglect’ people with high levels of support needs.

'Autistic people need better access to quality autism assessments and tailored support.

'The real debate about autistic people is how to address the chronic inequalities they face. It is unhelpful and a false choice to pit autistic people against each other – getting the right support early and better understanding makes a big difference to all autistic people.'