Majority of people aged over 40 with autism are undiagnosed, new study finds

A groundbreaking new review from King's College London has revealed that autistic adults in their middle age and beyond are battling with undiagnosed autism and encountering a host of mental and physical health problems too. The research also uncovered staggering gaps in autism studies focusing on older people with the condition.

Published in the Annual Review of Developmental Psychology, the investigation revealed that roughly 23% of people under 19 with autism are thought to remain undiagnosed. In comparison, 96% of autistic people over 60 have never received a diagnosis.

This older demographic showed the highest rates of missed diagnoses, with 96.29% of autistic men and 97.19% of autistic women over 60 failing to receive proper diagnosis.

The 40 to 59 age bracket followed closely behind, where 91.45% of autistic men and 79.48% of autistic women remained undiagnosed. In the 20 to 39 age range, diagnostic rates improved dramatically, leaving just 53.17% of autistic men and 49.27% of autistic women without recognition.

The study concluded that autistic adults beyond 40 years old are 89% undiagnosed overall.

Dr Gavin Stewart, British Academy Postdoctoral Research Fellow at the IoPPN and principal author of the review, said: "These very high underdiagnosis estimates suggest that many autistic adults will have never been recognised as being autistic, and will have not been offered the right support. This could make them more susceptible to age-related problems, for example being socially isolated and having poorer health.

"The high rates of underdiagnosis also mean that much of our research has systematically overlooked a large proportion of the autistic population, potentially skewing our understanding of how autistic people age, and leaving critical gaps in policy and services."

The research revealed that middle-aged and older autistic people experience higher rates of nearly all physical and mental health conditions compared to non-autistic adults.

These include immune diseases, cardiovascular disease, neurological disorders, gastrointestinal disorders, anxiety and depression, alongside conditions linked to advancing age, including Parkinson's disease, cognitive disorders, osteoporosis and arthritis.

Older adults displaying high autistic traits were also six times more prone to experiencing suicidal ideation, thoughts of self-harm and self-harm.

The results further indicated these adults were four times more likely to receive an early onset dementia diagnosis than non-autistic people. Autistic adults experienced worse outcomes in employment before retirement, relationships and overall quality of life, owing to high levels of social isolation.

The review also discovered they encountered obstacles to accessing healthcare support because of autistic characteristics such as communication differences, sensory sensitivities, uncertainty about service access and limited knowledge of autism in adulthood among medical professionals.

Professor Francesca Happé, Professor of Cognitive Neuroscience at the IoPPN and co-author of the review, added: "Understanding the needs of autistic people as they age is a pressing global public health concern. As autistic people age, the nature of the challenges they face changes. We must adopt a lifespan approach that funds long-term research, integrates tailored healthcare, and expands social supports so that ageing autistic people can live happy and healthy lives."

The researchers called for more studies and investigations to better understand the experiences of autistic people in midlife and older age. This can help improve outcomes for autistic people as they age.

If you believe you have signs of autism, the NHS recommends speaking to a health professional such as a GP and ask about being referred for an autism assessment. This is conducted by autism specialists who may ask about problems you are having, speak to people you know or observe how you interact with other people.

Receiving a diagnosis can provide clarity on why your perception and experiences of the world differ from others, enable you to access support and potentially even financial benefits. It can also assist in explaining to others why you perceive and experience the world differently.