Diagnostic Overshadowing

What is diagnostic overshadowing?

Diagnostic overshadowing happens when a healthcare professional attributes new or changing symptoms to an existing diagnosis, rather than investigating them properly. One condition “overshadows” the recognition of another.

For neurodivergent people, this is a serious and well-documented problem. It means physical illnesses, mental health conditions, and additional neurodevelopmental differences can go unrecognised for months or years - sometimes with life-threatening consequences.

It works in multiple directions. An autistic person’s anxiety might be dismissed as “just part of their autism.” A person with ADHD might have depression overlooked because their low mood is attributed to executive functioning difficulties. Physical pain in someone with a learning disability might be interpreted as “challenging behaviour” rather than investigated as illness.

Why this matters

The consequences of diagnostic overshadowing go far beyond inconvenience. Research consistently shows it contributes to poorer health outcomes and, in some cases, earlier death.

People with neurodevelopmental conditions experience the same range of physical and mental health problems as everyone else. But when their symptoms are filtered through the lens of an existing diagnosis, treatable conditions can be missed entirely.

In mental health services, the picture is equally concerning. A 2024 UK study found that 37.7% of people experiencing first-episode psychosis were likely neurodivergent - significantly higher than previous estimates. These individuals used urgent mental health services more frequently and spent twice as long in hospital, suggesting their needs were not being met through standard pathways.²

How it affects neurodivergent people

Physical health overlooked

When an autistic person who communicates differently presents with pain, their distress signals may not look like what clinicians expect. Head-banging, increased stimming, withdrawal, or changes in eating can all indicate physical illness - but they are frequently interpreted as “autistic behaviour” rather than investigated medically.

This is not hypothetical. There are well-documented cases of broken bones, dental abscesses, ear infections, and appendicitis going undiagnosed in autistic people because their pain presentation was attributed to their neurodevelopmental condition.

The NHS England clinical guide for frontline staff now explicitly warns against this pattern, reminding clinicians that “people with a learning disability and autistic people experience the same illnesses as anyone else” and that symptoms may simply be communicated differently.³

Mental health conditions missed

Neurodivergent people are at significantly elevated risk of anxiety, depression, OCD, eating disorders, and trauma-related conditions. Yet these are routinely missed because their symptoms overlap with - or are attributed to - the existing neurodevelopmental diagnosis.

For example:

• Anxiety in autistic people may present as avoidance, rigidity, or meltdowns - all of which can be dismissed as “autistic traits” rather than recognised as a separate, treatable anxiety disorder
• Depression in people with ADHD can look like low motivation, withdrawal, or difficulty completing tasks - easily confused with executive functioning challenges
• Trauma responses in neurodivergent people may be attributed to the neurodevelopmental condition itself, meaning the trauma goes unaddressed
• OCD in autistic people can be confused with autistic routines and rituals, despite requiring very different treatment approaches

One neurodevelopmental condition masking another

Diagnostic overshadowing also operates between neurodevelopmental conditions. A child diagnosed with ADHD may have their autistic traits attributed entirely to ADHD. An autistic person’s dyspraxia or dyslexia may be overlooked because “they already have a diagnosis.”

NICE surveillance evidence found that children diagnosed with ADHD first experienced significant delays in receiving an autism diagnosis, often not being identified until after age six. This matters because earlier recognition enables earlier support.⁴

The same pattern applies in reverse. Autistic people’s attention difficulties, impulsivity, or emotional dysregulation may be attributed to autism alone, when ADHD is also present and would benefit from its own treatment pathway.

Who is most affected?

Women and girls

Diagnostic overshadowing disproportionately affects women and girls. Girls with high autistic traits are particularly vulnerable to having their anxiety and depression attributed to their neurodevelopmental profile rather than recognised and treated independently. Masking - hiding neurodivergent traits to appear neurotypical - compounds this further, because clinicians may see a person who “does not look autistic” and dismiss co-occurring conditions.

People with learning disabilities

The concept of diagnostic overshadowing was first identified in the context of learning disabilities, where physical and mental health symptoms are routinely attributed to the disability itself. Adults with learning disabilities experience avoidable causes of death at more than twice the rate of the general population.¹

People with multiple diagnoses

When someone already has two or three diagnoses, there can be a clinical reluctance to “add another one.” This means that the fourth or fifth condition - which may be the one causing the most distress - goes unrecognised.

People in crisis

During mental health crises, neurodivergent people’s communication differences, sensory needs, and atypical presentations of distress can all contribute to overshadowing. Emergency settings, with their time pressures and unfamiliar environments, are particularly high-risk for this.

What the evidence says

UK policy recognition

Diagnostic overshadowing is now recognised at a policy level in the UK. Key developments include:

• The Royal College of Psychiatrists (CR228) report on the psychiatric management of autism in adults explicitly addresses diagnostic overshadowing, noting that comorbid disorders may go unrecognised when all symptoms are attributed to autism5
• The British Psychological Society (2021) guidelines on working with autistic people highlight the risk that a neurodevelopmental diagnosis can lead to overshadowing of other life elements6
• NHS England published frontline clinical guidance addressing diagnostic overshadowing in people with learning disabilities and autism3
• The Oliver McGowan Mandatory Training on learning disability and autism, recommended by the government for all healthcare staff, includes components on diagnostic overshadowing awareness
• The Parliamentary Office of Science and Technology (POST) published a briefing note in October 2024 on support for neurodivergent people, recognising barriers to healthcare access7

Research gaps

Despite growing recognition, there remain significant research gaps. A meta-analysis of studies on anxiety and depression in autistic adults found that only 4 of 36 studies even considered the possibility of diagnostic overshadowing - suggesting the phenomenon is widespread but under-researched.⁵

What you can do

Diagnostic overshadowing is a systemic problem, and it should not fall to individuals to fix it. But there are practical steps that can help you get the care you need.

Before appointments

• Write your concerns down in advance. Be specific about what has changed and when. “I have been feeling more anxious than usual for the past three months” is more effective than “I have been struggling.”
• Separate your symptoms by condition. If you have ADHD and are experiencing something new, say so clearly: “This is different from my usual ADHD presentation.”
• Prepare a baseline document. A short written summary of what is “normal” for you - your typical energy levels, sleep patterns, mood, and behaviours - helps clinicians recognise when something has changed.
• Bring someone who knows you. A friend, family member, or support worker who can confirm that your presentation has changed can be powerful evidence.

During appointments

• Name the concern directly. You can say: “I am worried that my symptoms are being attributed to my autism/ADHD without being investigated separately. Can we explore other possibilities?”
• Ask for investigations. If a physical symptom is being dismissed, ask: “Can we rule out other causes before attributing this to my existing condition?”
• Request written records. Ask for a copy of the clinic letter or a summary of what was discussed and decided.

If you are not being heard

• Request a second opinion. You have the right to ask for a referral to a different clinician.
• Use PALS (Patient Advice and Liaison Service). Every NHS trust has a PALS service that can help resolve concerns.
• Contact an advocacy service. Organisations like VoiceAbility and POhWER provide free NHS advocacy.
• Make a formal complaint. If you believe diagnostic overshadowing has led to a missed diagnosis or harm, you can complain through the NHS complaints process.

Keep your own records

Maintaining your own health records can be a powerful tool against diagnostic overshadowing. Document your diagnoses, medications, symptoms, and what your baseline looks like. When you can show a clinician clear evidence that something has changed, it is harder for symptoms to be dismissed.

For healthcare professionals

If you work in healthcare, understanding diagnostic overshadowing is essential for providing safe and effective care to neurodivergent patients.

Key principles:

• Investigate new symptoms independently. Do not assume they are explained by an existing diagnosis without proper assessment.
• Ask about baselines. Carers, family members, and the person themselves can tell you what is typical for them and what has changed.
• Use communication passports and healthcare passports. These contain vital information about how the individual communicates and presents.
• Screen for co-occurring conditions. Actively screen for anxiety, depression, OCD, and trauma in neurodivergent people rather than waiting for them to raise it.
• Complete the Oliver McGowan Mandatory Training if you have not already done so.
• Make reasonable adjustments. Longer appointments, written information in advance, sensory-friendly environments, and clear communication all support accurate diagnosis.

Where to find support

Organisations

• Dimensions UK - campaigns on health inequalities for people with learning disabilities and autism, including the “My GP and Me” campaign
• Mencap - support for people with learning disabilities, including health advocacy
• National Autistic Society - information on healthcare access for autistic people
• ADHD UK - support and advocacy for people with ADHD
• VoiceAbility - free NHS advocacy services across England

neurobetter resources

• Our Local Services directory can help you find NHS and private providers near you
• Our Ask a Counsellor service lets you put a question to a registered counsellor
• Our Online Community connects you with other neurodivergent people who understand