Yes, dementia can be and frequently is misdiagnosed — and the error rates are higher than most people assume. Research drawing on a database of more than 900 patients found that roughly one in four Alzheimer’s diagnoses may be incorrect. A separate line of research published in 2024 found that nearly 13 percent of people diagnosed with dementia actually had a treatable condition that was mistaken for an irreversible neurodegenerative disease. These are not edge cases. They represent a systemic challenge rooted in the complexity of the brain, the overlap between dementia and dozens of other conditions, and the diagnostic tools currently available to clinicians.
Consider a 72-year-old woman brought to her doctor with memory lapses, slowed thinking, and withdrawal from daily activities. Her physician orders a cognitive screening test, she scores in the impaired range, and a diagnosis of Alzheimer’s disease follows. What may go undetected is that she has been taking a sleep aid with anticholinergic properties for years, or that she has an undiagnosed vitamin B12 deficiency, or that she is in the grip of a severe depressive episode that mimics dementia so closely it even has a clinical name: pseudodementia. Each of those conditions is reversible. A wrong diagnosis of Alzheimer’s sends a patient down a path of irreversible prognosis, inappropriate treatment, and lost time to actually address what is wrong. This article covers how common misdiagnosis is across different dementia subtypes, which conditions are most frequently confused with dementia, what drives diagnostic error, and what families can do about it.
Table of Contents
- How Often Is Dementia Actually Misdiagnosed?
- What Conditions Are Most Commonly Mistaken for Dementia?
- Why Frontotemporal and Lewy Body Dementia Are Especially Prone to Error
- The Role of Diagnostic Delays in Making Misdiagnosis Worse
- What Drives Diagnostic Error — And Who Is Most at Risk
- When a Second Opinion Changes Everything
- Where Dementia Diagnosis Is Headed
- Conclusion
- Frequently Asked Questions
How Often Is Dementia Actually Misdiagnosed?
The honest answer is: more often than the medical system comfortably acknowledges. The figure most cited in recent literature comes from a study using the National Alzheimer’s Coordinating Center Uniform Data Set, which found approximately 25 percent of Alzheimer’s diagnoses were incorrect. That study examined clinical diagnoses against autopsy or biomarker confirmation, which is the closest thing medicine has to ground truth in this field. One in four is not a small margin of error for a diagnosis that typically carries a terminal prognosis and shapes every major life decision a person and their family will make going forward. The misdiagnosis problem is even more pronounced with rarer subtypes of dementia.
A February 2025 study from the University of Queensland found that nearly 70 percent of patients suspected of having frontotemporal dementia did not actually have the disease after thorough evaluation. Dementia with Lewy bodies presents a different but equally striking pattern: research published in the Journal of the Neurological Sciences found that in patients without accompanying parkinsonism, approximately 75.8 percent of Lewy body cases were initially misidentified as Alzheimer’s disease. These numbers reflect how much diagnostic confidence can diverge from diagnostic accuracy, particularly outside of major academic medical centers with dementia subspecialty care. What makes these figures especially important is the downstream consequence. Getting the wrong diagnosis is not a bureaucratic problem — it determines whether someone receives antipsychotic medications that can be severely harmful or even fatal to Lewy body patients, whether a treatable depression goes unchecked, or whether a surgically correctable condition like normal-pressure hydrocephalus is never addressed. The stakes of misdiagnosis are not abstract.
What Conditions Are Most Commonly Mistaken for Dementia?
The list of conditions that can convincingly mimic dementia is longer than most people expect, and that is precisely what makes the diagnostic picture complicated. Depression is perhaps the most common culprit. In older adults, depression frequently presents not with visible sadness but with cognitive slowing, memory difficulties, social withdrawal, and flat affect — a cluster of symptoms that maps closely onto early dementia. The term pseudodementia was coined to describe this phenomenon, and while some clinicians consider the term outdated, the clinical reality it describes remains very much active. A full depressive episode can produce scores on standard cognitive assessments that look indistinguishable from mild to moderate Alzheimer’s disease. Medication side effects are another major and underappreciated driver. Research suggests that drug-induced cognitive impairment may account for up to 12 percent of suspected dementia cases.
Sleep aids, benzodiazepines, anticholinergic drugs used for bladder control or allergies, and certain anti-anxiety medications can each impair memory, attention, and processing speed in older adults. The problem is compounded by polypharmacy — the more medications an elderly patient takes, the higher the cumulative cognitive burden and the harder it becomes to trace cognitive decline back to any single agent. Other conditions on the list include delirium from infection or metabolic disturbance, vitamin B12 deficiency, thyroid disorders (both hypothyroidism and hyperthyroidism), urinary tract infections in elderly patients, normal-pressure hydrocephalus, and hepatic encephalopathy in patients with advanced liver disease. However, it is important not to swing to the opposite extreme. Not every dementia diagnosis deserves reflexive skepticism. The existence of mimicking conditions does not mean that most people diagnosed with dementia are actually fine. What it means is that the diagnosis warrants careful evaluation and should not rest on a single office visit or a brief cognitive screening test alone. If a patient scores poorly on a cognitive test but also has a severe untreated UTI, correcting the infection first and retesting is not cautious overthinking — it is good medicine.
Why Frontotemporal and Lewy Body Dementia Are Especially Prone to Error
Frontotemporal dementia occupies a peculiar diagnostic position. Unlike Alzheimer’s disease, which typically presents first with memory problems, FTD often begins with personality changes, impulsivity, disinhibition, compulsive behaviors, or language difficulties. These symptoms look far more like psychiatric illness than like the dementia most clinicians are trained to recognize. As a result, FTD patients frequently receive diagnoses of bipolar disorder, depression, obsessive-compulsive disorder, or personality disorder for years before anyone investigates a neurodegenerative cause. Research published in Frontiers in Neurology documented this pattern explicitly — psychiatric misdiagnosis is the norm, not the exception, in early FTD. The University of Queensland’s 2025 study found that among patients referred to a specialist clinic with a suspected FTD diagnosis, nearly 70 percent turned out not to have the disease at all.
That finding reflects two overlapping problems: the difficulty of identifying true FTD in its early stages, and the difficulty of ruling it out once it has been suspected. When a patient has been behaving erratically for two years and carries a documented psychiatric history, it takes real diagnostic persistence to go back and reconsider the whole picture from the ground up. Dementia with Lewy bodies suffers from a different kind of invisibility. It shares memory impairment with Alzheimer’s but also involves fluctuating cognition, visual hallucinations, and motor symptoms that may not emerge immediately. The fluctuating nature of cognitive impairment in DLB is often dismissed as inconsistency or anxiety rather than recognized as a hallmark feature. When motor symptoms are absent — which occurs in a meaningful subset of patients — the cognitive profile looks enough like Alzheimer’s that the more dangerous diagnosis is routinely missed. This matters acutely because certain medications, particularly antipsychotics, can trigger life-threatening reactions in DLB patients.
The Role of Diagnostic Delays in Making Misdiagnosis Worse
Even before a misdiagnosis formally occurs, the path to any diagnosis at all is slow. Research from Michigan State University found that the average time from first dementia symptoms to an actual diagnosis is 3.5 years. For people with early-onset dementia — those under 65 — the delay stretches to 4.1 years. In that window, patients are often told their symptoms are normal aging, stress, or a byproduct of other health issues. Each year of delay is a year in which treatable causes go untreated, and in which irreversible conditions progress without any management. The comparison between early-onset and late-onset cases is instructive.
Younger patients who develop dementia symptoms are frequently not taken seriously precisely because their age makes dementia seem unlikely. A 58-year-old who struggles to find words or manage finances at work may be told they are burned out or anxious before anyone orders neuroimaging. By the time a diagnosis is finally made, years of potential early intervention — or identification of a treatable cause — have passed. Meanwhile, older patients face a different bias: their symptoms are normalized as an expected part of aging, which delays workup in a different way. For families navigating this, the practical tradeoff is between accepting a diagnosis that feels uncertain versus pursuing a second opinion or additional testing, which takes time and effort, often at a moment when the patient and family are already exhausted and emotionally depleted. But the data on misdiagnosis rates makes a strong case that the effort is warranted, particularly if the initial evaluation was brief, if no specialist was involved, or if the diagnosis does not match the pattern of symptoms the family has actually observed.
What Drives Diagnostic Error — And Who Is Most at Risk
Several factors consistently appear in the literature on dementia misdiagnosis. One is prior psychiatric history. When a patient has a documented record of depression, anxiety, or other psychiatric diagnoses, clinicians are more likely to interpret new cognitive symptoms through that existing lens rather than consider a neurological cause. The reverse also occurs: patients with true dementia who develop behavioral symptoms may have those symptoms attributed to psychiatric illness rather than to the underlying disease. Misinterpretation of diagnostic tools is another driver. Brain imaging studies like MRI or PET scans provide important data, but they require expert interpretation, and findings that appear subtle can be dismissed or misread.
Standard cognitive tests like the Mini-Mental State Examination or the Montreal Cognitive Assessment are useful screening instruments, but they have real limitations. They can be failed by people with low education, anxiety, or language barriers who do not have dementia, and they can be passed by people in early stages of frontotemporal or Lewy body disease who retain verbal and calculation skills while losing insight and social judgment. The warning here is practical: a normal cognitive test score is not a reliable rule-out for dementia, and an abnormal one is not a reliable confirmation. Both results require context. A single general practitioner appointment with a brief screening tool is the standard initial workup in many healthcare systems, but it is not adequate as a standalone basis for a diagnosis as consequential as dementia. Patients and families who push for neurologist referrals, comprehensive neuropsychological testing, and imaging are not being difficult — they are asking for what the evidence says is needed.
When a Second Opinion Changes Everything
The experience of patients who pursue second opinions after a dementia diagnosis is revealing. In cases where the initial diagnosis was made quickly or based primarily on cognitive test performance, specialist review — particularly at a memory clinic or academic medical center — frequently results in a revised or refined diagnosis. This does not mean every general practitioner gets it wrong, but it does mean that subspecialty evaluation adds something that a single generalist visit cannot replicate. Consider the case of normal-pressure hydrocephalus, a condition in which excess cerebrospinal fluid accumulates and causes a triad of cognitive impairment, gait disturbance, and urinary incontinence.
The cognitive symptoms can closely resemble Alzheimer’s disease, and the condition is often missed unless the examining physician is specifically looking for the full symptom cluster and orders appropriate imaging. When identified correctly, NPH is surgically treatable with a shunt that can dramatically improve or reverse cognitive symptoms. Patients who were told they had Alzheimer’s and were declined for any treatment have in some cases recovered meaningful function after surgical correction of NPH. That outcome is impossible if the original diagnosis is never questioned.
Where Dementia Diagnosis Is Headed
The diagnostic landscape is changing, though not as fast as the problem demands. Blood-based biomarker tests — particularly plasma phosphorylated tau assays — are increasingly being validated as tools that can detect Alzheimer’s pathology years before symptoms appear and can help distinguish Alzheimer’s from other causes of cognitive impairment. As these tests move from research settings into clinical practice, the rate of misdiagnosis should, in theory, decline. The same is true for expanded access to PET imaging that can visualize amyloid plaques and tau tangles in living patients.
What is less certain is how quickly these advances will reach the community clinics, rural hospitals, and underserved settings where most dementia diagnoses are actually made. Academic medical centers with memory disorder specialists already have access to tools and expertise that most patients will never encounter. Addressing misdiagnosis at a population level requires not just better technology but broader clinical training, updated referral protocols, and a cultural shift in how both physicians and patients approach the differential diagnosis of cognitive decline. The science is moving forward. The translation into standard care is slower, and in that gap, misdiagnosis continues.
Conclusion
Dementia misdiagnosis is not rare. Approximately one in four Alzheimer’s diagnoses may be incorrect, nearly 70 percent of suspected frontotemporal dementia cases turn out to be something else, and a significant proportion of people told they have an irreversible brain disease are actually living with depression, medication toxicity, thyroid dysfunction, or another treatable condition. The average patient waits 3.5 years just to receive any diagnosis at all — a window in which treatable causes quietly worsen or go unaddressed. These numbers carry real weight for anyone navigating a new or suspected dementia diagnosis for themselves or a family member. The practical takeaways are not complicated but they require persistence.
If a diagnosis was made quickly, without specialist involvement, or does not fit the actual pattern of symptoms, a second opinion is reasonable and often warranted. Ask about reversible causes. Ask whether medications could be contributing. Ask whether a full neuropsychological evaluation or specialist imaging has been considered. A dementia diagnosis should be the conclusion of a thorough process, not the starting assumption. For a disease with the stakes this high, that standard is not too much to ask.
Frequently Asked Questions
Can a doctor be certain someone has Alzheimer’s disease without an autopsy?
Not with complete certainty, even today. Definitive Alzheimer’s diagnosis has historically required post-mortem examination of brain tissue. However, newer biomarker tests — including PET imaging and blood-based plasma tau assays — are increasingly able to detect Alzheimer’s pathology in living patients with high accuracy. These tests are not yet universally available but are becoming more common in specialist settings.
What is the difference between dementia and delirium?
Delirium is an acute, usually reversible state of confusion that develops rapidly — often over hours or days — in response to an underlying cause such as infection, medication change, surgery, or metabolic imbalance. Dementia develops gradually over months or years. The two can coexist, and delirium in an older adult can be mistaken for dementia progression, particularly if the underlying cause is not identified and treated.
If my parent was diagnosed with dementia but the symptoms don’t match what the doctor described, what should we do?
Request a referral to a neurologist or geriatric psychiatrist, ideally one with subspecialty training in memory disorders. Ask specifically whether reversible causes — medication side effects, depression, thyroid function, vitamin B12 levels, and imaging for conditions like normal-pressure hydrocephalus — have been formally evaluated and documented. A second opinion at a memory clinic or academic medical center is reasonable and should not require an apology.
Are certain dementia types more likely to be misdiagnosed than others?
Yes. Alzheimer’s disease, while frequently diagnosed, is misidentified roughly 25 percent of the time. Frontotemporal dementia and dementia with Lewy bodies carry much higher misdiagnosis rates. FTD is routinely mistaken for psychiatric illness, and Lewy body dementia is frequently misclassified as Alzheimer’s, particularly in cases without prominent motor symptoms.
Can medication cause someone to appear to have dementia?
Yes, and this is more common than widely recognized. Anticholinergic medications, benzodiazepines, sleep aids, and certain anti-anxiety drugs are among the most frequently implicated. Medication-related cognitive impairment may account for up to 12 percent of suspected dementia cases. Reviewing and adjusting medications — ideally with a geriatrician or pharmacist experienced in older adult care — can sometimes produce significant cognitive improvement.
Is pseudodementia a real condition?
The term pseudodementia refers to the cognitive impairment that can accompany severe depression, particularly in older adults. The cognitive deficits are real — they show up on testing and significantly affect daily function — but they are caused by the depressive illness rather than neurodegeneration. When the depression is treated effectively, cognitive function typically improves. Because the presentation overlaps substantially with early Alzheimer’s disease, depression is one of the most important conditions to rule out before a dementia diagnosis is finalized.
