Autism diagnoses ‘increasingly linked to also having ADHD or anxiety’

Jane Kirby, Press Association Health Editor

Autism diagnoses in the UK are being increasingly linked to also having conditions such as ADHD or anxiety, new research has suggested.

Experts found a decline in people being diagnosed with autism who also had conditions such as epilepsy and intellectual disability, and a rise in people who also suffered things like stress, eating disorders, headaches and chronic fatigue.

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.

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.

Further analysis showed a change in the make-up of people newly-diagnosed with autism.

“Over time, there has been a consistent decline in the proportion of autistic adults with a prior diagnosis of epilepsy, psychosis and intellectual disability, and an increase in the proportion with a prior diagnosis of attention-deficit hyperactivity disorder (ADHD), anxiety, depression and several other mental illnesses,” researchers said.

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, as well as use of antidepressants, melatonin (for sleeplessness), opioids and gabapentin (a drug for epilepsy and nerve pain).

In one example, the proportion of autistic adults with prior records of epilepsy in the UK decreased from 10% in 2010 to 4% in 2023.

Meanwhile, those with a history of anxiety increased from 28.7% to 58.3%.

The team included experts from the Medical Research Council’s integrative epidemiology unit at the University of Bristol and Avon and Wiltshire Mental Health Partnership NHS Trust.

They said there could be several potential explanations for the findings.

“First, most of these conditions have also increasingly been diagnosed among adults without prior autism diagnoses in both our study and in national surveys – we can expect autistic adults to also be subject to these temporal trends,” the team said.

“Second, changes to diagnostic manuals mean that clinicians may be more willing to recognise co-occurring conditions and diagnose autism for those with other prior mental health conditions.

“Relatedly, 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.

“Conversely, a greater tendency to misattribute features that are typical of other conditions to autism cannot be ruled out.

“Together, the trends found in this study appear to reflect the changing context in which clinicians make diagnoses.”

The team said that, whatever the cause, “efforts will need to be made to recognise and address the needs (of autistic people) with appropriate support”.

In the UK, 24.5 million adults contributed to the study, including 141,119 with an autism diagnosis.

In Sweden, more than nine million were involved, of whom around 100,000 had an autism diagnosis.

A first recorded adult autism diagnosis was consistently higher in Sweden than the UK, but incidence increased rapidly in the UK after 2020.

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”.

“However, the possibility of other mental health presentations associated with camouflaging to be misidentified as autism, and in part contributing to the rapid increases in diagnosis rates among females, cannot be ruled out.”

Autism is a neurodevelopmental condition in which people can struggle with communication and may have restricted, repetitive patterns of behaviours and interests.

Last month, a Government-ordered review concluded the UK is at a “tipping point” where people are at risk of being misdiagnosed with ADHD and autism.

It suggested a mismatch between the true rates of ADHD and autism in society and the numbers seeking help for the conditions.

They also pointed to pressure for diagnosis from private providers and called for tighter restrictions on those carrying out assessments for the conditions.

The team said overdiagnosis can lead to “over-medicalisation” where ordinary, healthy, life experiences are turned into medical problems.

“Most people are sometimes inattentive, anxious or socially uncomfortable,” the report stated.

“Having ADHD or autism-related traits does not necessarily mean someone has a diagnosable condition.”

Review chairman Professor Peter Fonagy said “life has become harder” for young people because it is “more uncertain, more relentlessly observed and appraised, with less belonging and fewer opportunities to take time out, to recuperate and recover”.

The head of the division of psychology and language sciences at UCL added: “There is a real rise in distress and it’s substantial, and is genuine, and there are a range of drivers.”