Diagnostic overshadowing: when a label hides the rest

A 48-year-old man with schizophrenia arrives at the emergency department agitated, saying his chest feels tight. Triage reads the old diagnosis on the screen before hearing the complaint. Someone comments that he has come in other times "for anxiety". The hypothesis of a psychiatric crisis gains strength in seconds, and the electrocardiogram waits.

This shortcut has a name: diagnostic overshadowing. It is what happens when a known diagnosis starts to explain everything that comes after. This text shows who is most at risk, what the research found and what you can do in the consultation and in the service so that the old label helps you think instead of ending the reasoning.

Key points

• Diagnostic overshadowing is attributing symptoms of a new disease to a diagnosis the patient already has (Hallyburton, 2022).
• People with mental illness, substance use, intellectual disability, autism or dementia are among the most exposed (van den Bemd, 2024).
• In the emergency department, complex presentation, difficult communication, crowding and haste increase the risk (Shefer, 2014).
• People with a history in mental health services had more cancer diagnosed from an emergency (Cunningham, 2024).
• Delirium in someone who already has dementia often goes unnoticed (Nitchingham, 2021).
• A complete examination, listening to the caregiver and a simple question about what has changed help reduce the problem.

Summary

• What diagnostic overshadowing is
• Where overshadowing appears
• What the research shows
• Why the label wins
• How to recognize the risk in the consultation
• What to do: countermeasures in the consultation and in the service
• How NEXO helps train this reasoning
• Frequently asked questions
• Take-home messages

What diagnostic overshadowing is

A concept analysis gathered the literature that used the term and proposed a unified definition: the wrong attribution of symptoms of a disease to an already diagnosed comorbidity (Hallyburton, 2022). The same analysis recalls that the term was born in the field of intellectual disability, as a bias that affects judgment about conditions that appear together (Hallyburton, 2022).

Over time, the concept broadened. Today it describes any situation in which a striking diagnosis hides another, whether a physical disease behind a mental disorder or a second disorder behind the first (Becker-Haimes, 2023). The common point is salience: the diagnosis already in the chart takes the front of the scene and pushes the new signs to the background.

A neighboring text about stigma and language shows how the words in the chart feed this shortcut. Here the focus is different: overshadowing as a mechanism of diagnostic error, the groups in which it appears and the measures that reduce the risk in daily practice.

A reasoning error, and also a system error

Overshadowing is usually described as an individual bias, but it rarely depends only on the person providing care. Emergency department professionals interviewed pointed to direct factors, such as complex presentation, difficult communication and challenging behavior, and background factors, such as crowding, time pressure, targets and stigmatizing attitudes from a minority of the team (Shefer, 2014).

This two-layer reading matters. If the problem were only a lack of attention, it would be enough to ask for more care. Since it also arises from the environment, the response needs to include time, specialized support and routines that force a second look.

Where overshadowing appears

The mechanism is the same in different contexts, but each group has its own traps. Knowing these traps helps recognize the risk before it becomes a delay.

Severe mental illness

People with severe mental illness live less than the general population, and the concept analysis cites an average difference of 10 years, with more than two thirds of deaths attributed to heart disease and cancer (Hallyburton, 2022). A recent narrative review describes this mortality gap as persistent, despite advances in care, and includes overshadowing among the barriers to access (Wiesepape, 2025).

People who live with mental illness notice the problem. In a study with people who have experience of mental illness in four health systems, the feeling of not being taken seriously and experiences of stigma appeared in every setting (Schäfer, 2026). The study title sums up the complaint: having a mental illness does not stop someone from also having a physical illness.

Substance use

Alcohol and other drug use adds another strong label. In a survey of people with mental and substance use disorders who sought care for physical problems, a recurring theme was the assumption that physical symptoms, including pain, came from the disorder (Cunningham, 2023). Participants also reported that clinicians focused on mental health at the expense of physical health (Cunningham, 2023).

In practice, this shows up when confusion is read as intoxication without a glucose test, when abdominal pain becomes "medication seeking", or when a fall is labeled drunkenness without a neurological exam.

Intellectual disability

In intellectual disability, overshadowing means attributing symptoms to the disability itself rather than to a health problem (van den Bemd, 2024). Verbal communication may be limited, and pain or malaise show up as a change in behavior, refusal to eat or agitation.

In a study on chronic diseases in primary care, professionals relied on caregivers to get information about the disease and to explain the guidance in more suitable language (van den Bemd, 2024). The caregiver knows the baseline behavior, and it is precisely the change from that baseline that reveals the new problem.

Autism and other psychiatric diagnoses

Overshadowing also happens between psychiatric diagnoses. A review on autism describes how associated conditions, such as social anxiety and obsessive-compulsive disorder, can mask the core signs in people with milder symptoms, and how self-harm in autism is often interpreted as a personality disorder (Gupta, 2025).

An experiment with 266 mental health clinicians showed the same effect with trauma (Becker-Haimes, 2023). When the vignette included a traumatic event, participants considered the target diagnosis, such as obsessive-compulsive disorder or oppositional defiant disorder, less likely than in the same vignette without the trauma (Becker-Haimes, 2023). The trauma history took over the scene and reduced attention to the second problem.

Dementia and delirium

In older people with dementia, acute confusion can be read as the expected worsening of the underlying disease. Delirium is an acute and fluctuating change in cognition, mainly in attention, triggered by a medical illness or by substances, and the review on delirium superimposed on dementia estimates that delirium goes unrecognized in 43 to 76 of every 100 patients who have it (Nitchingham, 2021).

A study of nursing records analyzed 128 days of notes on patients with dementia who had delirium and found descriptions of confusion, lethargy, restlessness and fluctuation of mental status, but no record that the delirium had been recognized (Steis, 2012). The information was there; what was missing was the name that would lead to the search for the cause. The text on implicit bias discusses a similar shortcut, "it's just age".

What the research shows

The evidence on overshadowing comes from different designs, each with its own limits. Qualitative studies describe how the phenomenon happens, cohorts show worse outcomes in exposed groups, and vignette experiments isolate the effect of the label.

Study	Design and population	What it found	Main limit
Shefer, 2014	Interviews with 18 physicians and 21 nurses from the emergency department and consultation-liaison	Direct and background factors for the wrong attribution	Professionals' perception
Cunningham, 2024	National cohort of people with cancer	More diagnosis after an emergency visit in those with a mental health history	Association, without proof of cause
Cunningham, 2023	Survey of people with mental and substance use disorders	Physical symptoms and pain attributed to the disorder	Patients' report
Becker-Haimes, 2023	Experiment with 266 clinicians and vignettes	Target diagnosis less likely when there was trauma	Vignette differs from practice
Nitchingham, 2021	Review on delirium in dementia	Most delirium goes unrecognized	Heterogeneous studies
Steis, 2012	Analysis of 128 days of nursing records	Signs described without naming delirium	Small sample

Cancer diagnosed in the emergency department

The most concrete data comes from a national cohort that compared how four cancers were diagnosed. Emergency presentation was defined as admission in the 30 days before diagnosis, and those diagnosed this way have lower survival (Cunningham, 2024).

After adjustment for age, sex, ethnicity, area deprivation and stage, the rate of emergency presentation was higher in people with a history of using mental health or addiction services: relative risk of 1.19 for lung, 1.69 for prostate, 1.42 for breast and 1.31 for colorectal cancer (Cunningham, 2024). The authors cite overshadowing among the possible explanations, alongside stigma (Cunningham, 2024).

What professionals say

In emergency department interviews, the problems fell into three categories: difficulty obtaining the history, problems with the emergency environment and problems linked to labels and stigma (Shefer, 2014). The same professionals noted that a psychiatric consultation team available day and night helps reduce the risk of a wrong diagnosis (Shefer, 2014).

Limits of the evidence

Most of the data is qualitative or observational, and many studies come from services with their own organization, which limits generalization. Studies are lacking that test, with a comparison group, whether measures such as asking what has changed or reversing the handover actually reduce missed diagnoses. Until then, these measures rest on the logic of error and on the experience of teams. It is hard to measure how often overshadowing happened, because the error only appears when someone reviews the case later. Even so, the consistency between accounts from professionals, patients and cohorts supports the idea that the phenomenon is real and frequent enough to deserve attention.

Why the label wins

Overshadowing uses the same shortcuts that appear in other diagnostic errors. The old diagnosis acts as an anchor, and the explanation that already exists seems sufficient. Reasoning stops early, in a classic case of premature closure, because it found a plausible answer.

Emotion also weighs in. An agitated, repetitive or hostile patient stirs impatience, and affective bias shows how a negative label travels from one professional to another. When the handover begins with "it's the psychiatric patient in bed five", the next team already arrives with the conclusion ready.

From a cognitive standpoint, the label feeds fast reasoning. Dual process theory describes an intuitive mode, which recognizes patterns in seconds, and an analytical mode, slower and deliberate. The underlying diagnosis offers a ready pattern to the intuitive mode, and the analytical mode only comes into play if something draws attention. When the patient communicates with difficulty or the environment is crowded, that alarm takes time to sound, and the first explanation ends up being the last one too.

The environment closes the circle. Crowding, time targets and difficult communication reduce the willingness to examine again (Shefer, 2014). A palliative care review found overshadowing among the main challenges for people with intellectual disability or severe mental illness, alongside assumptions about decision-making capacity (Ashok, 2023).

How to recognize the risk during care

The first step is to notice when the situation favors the shortcut. Some signs deserve a pause before closing the case:

• the underlying diagnosis appeared before the complaint, on the screen or in the handover;
• the proposed explanation is "the usual" or "that's his condition";
• the patient or the caregiver says that this time it is different;
• vital signs or the physical examination are not yet complete;
• communication is difficult and the history depends on third parties;
• the team is irritated or in a hurry.

These signs indicate risk, not error. They show that it is worth taking a diagnostic pause and asking what else could explain the picture.

When the patient comes back several times

Frequent return visits are fertile ground for the shortcut. Each previous visit that ended with "anxiety attack" or "intoxication" makes it easier to repeat the conclusion, and the team may come to see the patient as someone who always comes for the same reason. The emergency professionals interviewed mentioned precisely the difficulty of obtaining the history and the weight of the label among the factors that lead to the wrong attribution (Shefer, 2014).

A practical way to break this cycle is to treat each visit as a new case at the start of the reasoning. Ask what brought the patient in today, what is different from the other times and whether any symptom is new. Compare the vital signs with previous records. A heart rate that never went above 90 and is now 120 is a clue that the history helps to see, not to hide.

The shift handover

The shift handover concentrates risk because it sums the patient up in a few words. When the first piece of information is the psychiatric diagnosis or the disability, whoever receives the case already starts with a ready-made hypothesis. It is worth reversing the order: current complaint, relevant findings, what is still pending and, finally, the underlying conditions that may interfere with the assessment.

This order also protects the person handing over the case. By organizing what you say around the findings, you notice more easily what was left unexplained. If the answer to a new symptom is only the old diagnosis, this is the moment to flag the pending item for the next shift.

The question about what changed

The most useful question is often simple: what is different from usual? For a person with intellectual disability, the answer comes from the caregiver. For someone with dementia, it comes from the family or the team that knows the baseline state. For someone with mental illness, it comes from the patient, who often knows how to tell the familiar crisis from a new sensation.

A case to think about

A 72-year-old woman with moderate dementia arrives from the facility where she lives because she "is more confused". Her companion says that yesterday she recognized the caregivers and today she barely keeps her eyes open. The dementia label offers a ready-made explanation, but the change within hours, the drowsiness and the fluctuation suggest delirium, which calls for an active search for a clinical cause (Nitchingham, 2021). The next step is to examine her, check vital signs, review medications and look for infection, pain, urinary retention or metabolic change.

What to do: countermeasures in care and in the service

The measures below come from the studies cited and from the logic of the error itself. They work better combined, because they address different layers of the problem.

1. Listen to the complaint before reading the old diagnosis, whenever possible.
2. Complete the vital signs and a physical examination directed at the new complaint.
3. Ask the patient and the caregiver what has changed from usual.
4. Write at least one physical hypothesis for each physical complaint.
5. Ask for support from the psychiatric consultation service without transferring clinical responsibility.
6. Reassess when the picture does not improve as expected.

In care

Separating the complaint from the label is a trainable habit. When you summarize the case, start with the current findings and only then mention the underlying diagnosis. The technique of organizing several complaints helps when the list is long and the label tries to sum everything up.

Reassess without starting from scratch

Reassessing does not mean repeating every test. It means going back to the findings with another question: if the underlying diagnosis were erased from the chart, what would the main hypothesis be? This simple exercise forces you to look at the data on their own. If the answer differs from the current conclusion, the difference must be investigated before discharge.

Reassessment also applies to time. A picture attributed to the known disorder should follow the expected course of that disorder. When the agitation does not yield to the usual measures, when the pain moves or when new signs appear on examination, the initial explanation has lost strength and another hypothesis gains room.

In the service

Emergency professionals valued the psychiatric consultation available at all times, but asked for clearer rules on who is responsible for what (Shefer, 2014). People with mental illness pointed to greater autonomy and concrete support to change health habits as facilitators (Schäfer, 2026). The review on severe mental illness argues for person-centered care, with continuity, integration and dignity (Wiesepape, 2025).

For people with intellectual disability, information in plain language and communication guidance help professionals and patients deal better with chronic illness (van den Bemd, 2024). In palliative care, adapting team training to beliefs about mental illness is one way to avoid overshadowing (Ashok, 2023).

In training

Teaching can show the phenomenon with cases where the label points one way and the clues point another. Discussing in a group why the first hypothesis seemed so convincing helps the student recognize the shortcut next time. The feedback after the case turns the error into learning without blame.

How NEXO helps train this reasoning

In NEXO, the case of the day is fictional, with a real clinical presentation and up to six progressive clues, and you propose the diagnosis by looking for the code in ICD-10.

The limits on using the game are described on the NEXO economy page. If you research teaching of clinical reasoning, the page for researchers explains how to get in touch. Professionals who write or review cases find information under curation and under creators, and institutions can learn about the proposal on the partnerships page. Training differential diagnosis with clues and looking for the right code in ICD-10 complete this practice.

Frequently asked questions

What is diagnostic overshadowing?

It is the wrong attribution of symptoms of a new illness to a diagnosis the patient already has (Hallyburton, 2022). The old diagnosis explains everything, and the new cause goes uninvestigated.

Are overshadowing and diagnostic shadowing the same thing?

Yes, they are translations of the same term. Some texts also speak of diagnostic eclipsing. The concept is the same in all cases.

Who is most at risk?

People with severe mental illness, substance use, intellectual disability, autism and dementia are the most studied groups (van den Bemd, 2024). Any striking diagnosis, however, can hide another (Becker-Haimes, 2023).

Is there proof that overshadowing causes harm?

The evidence is indirect. People with a history in mental health services had more cancer diagnosed after an emergency visit, a path linked to lower survival (Cunningham, 2024). Overshadowing is one of the possible explanations, alongside stigma and access barriers.

How to avoid it on shift?

Listen to the complaint before reading the old diagnosis, complete the examination and ask what changed. Crowded, rushed environments increase the risk, so it is worth setting aside a short pause before discharge (Shefer, 2014).

What to do when the confusion appears in a person with dementia?

Treat the acute change as possible delirium until proven otherwise and look for the clinical cause. Much of the delirium superimposed on dementia goes unrecognized (Nitchingham, 2021).

Take-home messages

• Diagnostic overshadowing is letting an old diagnosis explain a new symptom without investigation.
• Mental illness, substance use, intellectual disability, autism and dementia are high-risk contexts.
• Crowding, haste and difficult communication favor the shortcut as much as individual bias.
• The question about what changed, asked to the patient or the caregiver, is one of the most useful tools.
• A complete examination, a physical hypothesis for a physical complaint and reassessment reduce the risk.
• The baseline diagnosis is a clue in the case, and clinical reasoning must also look at what it hides.

Want to train your reasoning from the clues, without ready-made labels? Play the case of the day on NEXO.

References

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