Autism diagnoses have risen 10-fold in the last decade or so, prompting fears of overdiagnosis. But alongside the surge in cases, researchers have noticed a change in characteristics in people with the neurodevelopmental condition.
Since 2010, UK adults with autism are increasingly being diagnosed with conditions such as ADHD, anxiety and eating disorders, new research has suggested. Prior to that, autistic adults were more often diagnosed with conditions such as epilepsy and intellectual disability.
How Autism Diagnoses Have Increased Over Time
Researchers analysed data from the UK and Sweden, and wrote in the journal BMJ Mental Health that autism diagnoses have risen consistently over time. In the UK, rates of new diagnoses increased from six per 100,000 people in 2010 to 64 per 100,000 in 2023.
They also found a rapid rise in autism diagnoses among 16 to 20-year-olds since 2010 in the UK, alongside a rise in women and white people, compared to other ethnicities. Over time, there has been a consistent decline in the proportion of autistic adults with a prior diagnosis of epilepsy, psychosis and intellectual disability, researchers observed.
This has coincided with an increase in the proportion with a prior diagnosis of attention-deficit hyperactivity disorder, anxiety, depression and several other mental illnesses. Overall, autism rose in people who had been previously diagnosed with anxiety, depression, sleep disorders, ADHD, stress-related disorders, eating disorders, headaches and chronic fatigue.
Shifting Co-Occurring Conditions and Patient Profiles
Rises were also seen in people using antidepressants, melatonin for sleeplessness, opioids and gabapentin, a drug for epilepsy and nerve pain. The team, including experts from the University of Bristol and Avon and Wiltshire Mental Health Partnership NHS Trust, said conditions like ADHD and anxiety have risen in adults without autism, so we can expect autistic adults to also be subject to these temporal trends, they said.
Changes to diagnostic manuals may mean people with other mental health conditions are now being diagnosed with autism. It is possible that there is greater appreciation of nuanced forms of autism that may have previously been labelled as other conditions due to overlapping features, particularly in females. But other conditions may also be misidentified as autism, the study team added.
Prof Dame Uta Frith, emeritus professor of cognitive development at UCL, who wasn't involved in the research, said the shift in co-occurring conditions among people with autism could be linked to when people were diagnosed. The results provide further evidence of a split between early and late diagnosed autism, she stated.
Cases with early diagnosed autism are linked with neurological signs, such as epilepsy and cognitive impairments. Cases with late-diagnosed autism are instead linked with prior mental health problems, such as anxiety and depression. It is precisely this group that accounts for the increase. She added that cultural changes in the meaning and use of the autism label, rather than biological changes, may also be playing a role.
Understanding Autism and Current Screening Tools
Around 700,000 people in the UK are believed to have autism, a lifelong condition that affects how they experience and interact with the wider world. Features include difficulties with communication and interaction, repetitive behaviours or limited interests. It can also affect learning and development.
There are those who suggest autism, as well as ADHD, is being overdiagnosed in the UK. To get an official autism diagnosis, you need to be assessed by a healthcare professional. But if you think your or your child might have the condition, there is a simple quiz called the AQ-10 that you can use to help support your suspicions.
The AQ-10 was developed by The Autism Research Centre at The University of Cambridge, and it is recommended to be used as an autism screening tool by the National Institute for Health and Care Excellence. The assessment tool, used by NHS doctors, does not confirm whether you are on the spectrum. Instead, it is used to screen people who might be. A version for children is also available.
Broader Government Reviews and Expert Perspectives
A major Government-commissioned review warned England is reaching tipping point, where people risk being wrongly told they have either of the two conditions. It claimed ordinary, healthy, life experiences are being turned into medical problems, with Prof Sir Simon Wessely, of King's College London, claiming this could harm children, making them believe they were incapable of doing something they might actually be able to do.
The new study used more than 24 million UK adults, including 141,119 with an autism diagnosis, and nine million people in Sweden, of whom around 100,000 had an autism diagnosis. The number of people with autism who also had epilepsy decreased, from 10 per cent in 2010 to four per cent in 2023. Meanwhile, those with a history of anxiety increased from 28.7 per cent to 58.3 per cent.
New diagnoses also rose fastest in females in both nations, as well as in people of white ethnicity in the UK. The researchers said the findings on women may indicate an improved recognition of female presentations of autism, including the use of masking and camouflaging behaviours, addressing historic underdiagnosis.
Dr Monique Botha, associate professor in social and developmental psychology at Durham University, who wasn't involved in the research, pointed out that previous studies show that autistic adults are more likely to experience depression, anxiety, self-harm, and suicidal thoughts. She explained these difficulties are likely linked to the discrimination, exclusion and reduced quality of life people with autism experience. This is particularly relevant to autistic women, she added. She said the increasingly extensive psychiatric histories seen in people who get an autism diagnosis may reflect diagnostic inequalities rather than changing diagnostic boundaries.
