Frégoli syndrome

1. Overview — What is Frégoli syndrome?

Frégoli syndrome (or Frégoli delusion) is a type of “delusional misidentification” within the group of Delusional Misidentification Syndromes (DMS). At its core, it is not just “mistaking someone for another person” in an ordinary sense, but rather the brain misinterpreting other people’s identities at a systemic level.

The central feature of Frégoli is that the patient firmly believes that:

“The many people they encounter in daily life (both familiar people and strangers)
are in fact one and the same person who is disguising themselves, changing faces, changing clothes, or taking on new roles in multiple guises.”

In the patient’s imagination, “this person” is usually not seen as an ordinary individual, but is perceived as:

Someone who is harassing or persecuting them

Someone who is spying on / secretly observing them

Or a former enemy / someone with whom there has been serious conflict in the past

Therefore, when they go outside, the world is no longer “a wide variety of people,” but becomes a world filled with that one person alone, constantly switching appearances: today as a nurse, tomorrow as a taxi driver, the next day as a shopkeeper at the corner.

When we compare this with Capgras syndrome (the belief that “a close person has been replaced by an impostor”), we can see that Frégoli looks like a near-complete “mirror image”:

Capgras = A person who should feel familiar appears “not to be the real person” → they are seen as a stranger in disguise.

Frégoli = People who are complete strangers, many of them, are instead believed to be “all the same familiar person” in a new disguise.

In short:

Capgras = “Someone close → becomes someone else.”

Frégoli = “Everyone else → becomes the same single person.”

In terms of psychiatric diagnosis, Frégoli is not classified as an independent disorder in DSM-5-TR or ICD-11, but is regarded as a “phenomenon” that exists within other primary disorders, such as:

Schizophrenia / Schizoaffective disorder

Bipolar disorder with psychotic features

Delusional disorder (especially the persecutory type)

Psychotic disorder due to another medical condition

Or psychosis due to substances/medications, such as Parkinson’s medications, recreational drugs, etc.

Thus, when clinicians write an actual diagnosis, they tend to phrase it more like:

Schizophrenia with Frégoli-type delusional misidentification

Or Psychotic disorder due to another medical condition, with Frégoli delusion

In real life, this condition often leads patients to:

Be suspicious that someone is “following” them all the time, even if it is just a stranger on the bus or in a shopping mall

Feel that convenience store staff, security guards, nurses, new coworkers — are “actually all the same person”

Some will even go so far as to directly ask or confront others: “Why are you following me?”

Many begin to avoid public places, change their place of residence, or call the police frequently because they believe they are truly being persecuted.

What makes Frégoli more than just being overthinking or normally paranoid is that:

High conviction – Patients believe 100% that all of this is real, not “Maybe I’m just overthinking.”

Resistance to evidence – Even if documents, witnesses, or others confirm that they are different people, the patient will create additional explanations to protect their original belief.

Clear impact on life – It causes problems in work, relationships, safety, and daily functioning.

Historically, the name “Frégoli” comes from Leopoldo Fregoli, an Italian actor in the late 19th to early 20th century who was famous for rapid costume and role changes on stage, changing faces and outfits so quickly that audiences could barely keep up. Early psychiatrists borrowed his name to label the condition in which “a single person seems able to change faces repeatedly in many ways.”

In terms of epidemiology, Frégoli syndrome is considered a rare condition when compared with other psychotic symptoms, such as auditory hallucinations or typical persecutory delusions. However, every case that is identified tends to be treated as requiring serious assessment, because it can be linked to both:

Brain diseases (stroke, dementia, brain injury, Parkinson’s medication, etc.)

And safety risks (for example, confrontations with strangers because the patient believes they are “that same person in disguise”).

If we put it simply, Frégoli syndrome is a condition in which
the brain improperly binds together “familiarity + fear + the identity of an enemy,”
leading the patient to interpret the entire world through the lens that:

“Whoever I meet… is actually that same person,
just switching bodies to mess with me.”

2. Core Symptoms — Core features

The key point of Frégoli syndrome is “seeing the world through the belief that many people = one person in disguise.”
The symptoms we observe in real life form a “pattern” of thinking, interpretation, and behavior that all revolve around this core.

2.1. Delusional misidentification (Frégoli theme) — The delusion that many people are one

This is the central heart of Frégoli:

The patient believes that
persons A, B, C… (coworkers / people in the mall / people on TV / people in the hospital)

are actually “one and the same person” who has:

Changed clothes

Changed hairstyle

Put on or taken off glasses

Used makeup, different outfits, or “acting” to conceal their identity

There is usually one main “character” in their mind, such as:

Someone with whom they have had problems in the past

A former romantic partner

A supervisor

A neighbor they already disliked

The patient will then believe that this person is “following them in various forms,”
for example:

“The night-shift nurse, the shopkeeper at the corner, and the woman who walked past me in the mall are all the same person… they just disguised themselves.”

What makes this a true delusion, and not just a brief mistaken idea, is that:

The level of conviction is very high
Even if others bring solid evidence (like ID cards, CCTV footage),
the patient still insists:

“Exactly, that just proves he prepared forged evidence in advance.”

The belief is broad and persistent
It is not just a fleeting thought lasting 1–2 hours,
but an interpretive framework for the world used in daily life, continuously for weeks, months, or longer.

It is tied to a narrative (story) that is systematized in their mind
For example:

“He works for a secret organization.”
“He is a stalker hired by my ex.”
“He is an old debtor who hates me, so he follows me around to ruin my reputation.”

In other words, it is not a random thought, but a storyline that is “internally coherent within their own universe.”

They believe the other person knows everything about them

Knows their daily schedule
Knows where they are going
Knows their social media accounts/passwords (in some cases)

In summary: in the patient’s world, there are not “many ordinary people,” but rather “one enemy” wearing many different skins moving among the crowd.

2.2. Hyperfamiliarity / Familiarity bias — Excessive sense of familiarity

This part is the raw inner “feeling experience” behind the delusion.

When the patient sees a stranger,

the brain sends the signal:

“They look very familiar… this must be him.”

But it is different from déjà vu in that:

Déjà vu = A vague feeling of familiarity with a situation/image, but the person still knows “I’m probably just imagining it.”

Frégoli hyperfamiliarity = A strong feeling of familiarity plus a firm belief that “this person is definitely that same person” → then it is extended into a full delusion.

We can imagine the steps in the patient’s mind:

They see a stranger in the mall →
The brain feels an unusually strong sense of familiarity with the face.

That familiarity is not “checked” by reasoning (because frontal control is malfunctioning),

so the usual process:

“Maybe they just look similar”

does not occur.

It instead becomes the conclusion:

“Ah… he has disguised himself again.”

From then on, every new stimulus that is perceived as even slightly similar —
for example, voice, mannerisms, perfume scent, similar clothing color —
gets placed into the pattern of being “this same person.”

Familiarity bias in cognitive terms means:

Normally, the brain must “balance”
between familiarity and other evidence.

But in Frégoli,
the scale is heavily tilted toward “familiarity”,
causing other evidence (such as major differences in height, build, or age)
to be downgraded in importance.

2.3. Paranoia + anxiety/agitation — Suspiciousness, anxiety, and agitation

Once the world is interpreted as “there is one person following me everywhere,”

it is almost inevitable that the patient will:

Feel unsafe all the time

Going to a mall = He might be around in yet another disguise.
Going to the hospital = This nurse is actually him.
Returning home = They are afraid of being ambushed.

Have a very high threat perception
Footsteps behind them → interpreted as “him.”

Experience accompanying physical symptoms:

Rapid heartbeat
Insomnia
Repetitive intrusive images and thoughts
Irritability toward family members, because they feel no one understands or believes their warnings

Real-life consequences include:

Avoiding public places

Not going to work
Stopping visits to malls/markets
Not daring to go out alone

Consuming more media about stalking / persecution / conspiracy theories,
which further reinforces the preexisting belief pattern.

The dangerous part is that paranoia + hyperfamiliarity tend to go together:

A stranger who “seems familiar” → is seen as an enemy →
feelings of suspicion and anger escalate much faster than in the average person.

2.4. Hostility / Risk behaviors — Risky and aggressive behaviors

Because the patient believes that “they are truly being persecuted,”
defensive responses or even counterattacks can appear “rational” within their world.

Examples of behaviors that may be seen:

Confronting strangers

Staring directly at them and asking:

“How long have you been following me?”

Or accusing them of spying / intending to do harm.

Threatening or using aggressive language

Shouting or cursing in public
Calling the police or local authorities repeatedly to report that someone is following them

Potential use of nearby objects as weapons

If the symptoms are severe and they feel they are nearing a “cornered” state,
fear can transform into preemptive aggression:
“strike first to cut off the threat.”

Frequently changing residence / fleeing

Moving between rented rooms / houses / staying over at friends’ homes
Turning off their phone, cutting off certain channels of contact to “erase their trail”

Things clinicians must watch closely include:

Whether there has been any plan or attempt to use force in self-defense

Whether there is any history of harming someone because of these delusional beliefs

Whether the patient has prepared weapons (knives, sticks, other tools)

In articles aimed at the general public, it is important to emphasize that:

The patient is not inherently “evil” or “cruel.”

Their aggression is a product of real fear within a distorted belief system,
and for this reason, treatment and risk management are crucial.

2.5. Co-occurring psychiatric symptoms — The broader clinical picture

Frégoli almost never appears alone;
it usually comes as part of a “psychosis package” from an underlying disorder, such as schizophrenia, bipolar disorder with psychosis, or psychosis due to a medical condition, etc.

Commonly co-occurring features include:

Hallucinations

Auditory hallucinations
Hearing the voice of the person believed to be “that enemy” threatening, insulting, or commanding them.
Visual hallucinations
Seeing strange people in the house / outside the window and interpreting them as that person.

Thought disorder / disorganized thinking

Speech that jumps from topic to topic,
yet everything still revolves around the theme of “he’s following me.”
Connecting random events together:
a red car passing by → a shop sign → news on TV

becomes a “secret code” from the persecutor.

Mood symptoms

In bipolar disorder: there may be phases of abnormally elevated mood (mania/hypomania) or deep depression.
Severe paranoia can also lead to depression/hopelessness,
e.g., feeling that “no matter how I run, I can’t escape.”

Neurological symptoms

Unsteady gait / slurred speech / limb weakness (if due to stroke / brain lesion)
Problems with memory, planning, or sequential thinking (in dementia / TBI)

In summary: in real clinical assessment, doctors do not focus only on the sentence “He’s following me in disguise,”
but look at the entire set of psychiatric symptoms + neurological signs + medical/medication history together.

3. Diagnostic Criteria — Diagnostic framework (expanded for clinical / writing use)

This is very important:

Frégoli syndrome does not have its own separate diagnostic code in DSM-5-TR or ICD-11.

It is a “form of delusion of misidentification” that lives within primary disorders such as:

Schizophrenia
Schizoaffective disorder
Delusional disorder (persecutory type)
Bipolar disorder with psychotic features
Psychotic disorder due to another medical condition
Substance/Medication-induced psychotic disorder

Therefore, in practice, diagnosis proceeds in two levels, as we’ve outlined before. Here is the more detailed version.

Level 1: Confirming “Frégoli-type misidentification”

This is about answering the question:

“Is this truly the Frégoli theme, or just a temporary thought / a mere resemblance of faces?”

The components clinicians/clinical psychologists typically use as anchors:

1.1. The specific delusional content

Delusional content specific to Frégoli

The patient believes that many people (in various contexts)are “one person” who has disguised themselves / altered their appearance.
It is not just a feeling that someone looks similar,
but a firm conclusion that “this is the same person.”

The belief clearly contradicts evidence

There may be witnesses / documents / photographs confirming they are different people → yet the patient still does not believe.
The patient may generate “sophisticated explanations” to maintain the delusion, such as:
“

He has a team to help forge documents.”
“He has a twin / a team of secret agents helping him.”

Duration and stability of the belief

It persists for at least several days to weeks or more.
It is not just a transient confusion from delirium that lasts 1–2 hours and then disappears.

Impact on real life

It damages relationships (e.g., repeatedly accusing strangers at work).
Leads to loss of employment or academic problems.
Increases risk of confrontation with others / being stopped by police or security.
Or causes heavy expenditure of time/money on “escaping / protecting themselves from him.”

1.2. Distinguishing from ordinary “misperception”

During assessment, it is crucial to distinguish Frégoli from:

Ordinary people:

“That person really looks like my old university friend.”

but they still know that they might be mistaken / they do not believe it 100%.

People with social anxiety / autism:

They may over-interpret others’ gazes as staring / criticizing, which is an overinterpretation of intentions,
but they do not construct a story that this is “the same person in disguise.”

People who are intoxicated / briefly confused:

They may have hallucinations and disorientation,
but it resolves once their consciousness clears.

Frégoli delusion requires:
high conviction + persistence + systematic distortion in interpreting others’ identities.

Level 2: Identifying the underlying condition (Primary diagnosis)

Once it is confirmed that “yes, this is the Frégoli theme,” the next question is:

“Which disorder is this symptom sitting on?”

The clinician’s reasoning process is like a funnel:

2.1. Evaluating the broad framework: psychiatric vs neurological vs substance/medical

Psychotic disorders / Mood disorders

Does the history/presentation fit with:

Schizophrenia / Schizoaffective?
Bipolar I/II with psychotic features?
Delusional disorder (especially persecutory type)?

Are there other features such as hallucinations, disorganized speech/behavior, negative symptoms, mood episodes?

Neurocognitive / Neurological conditions

At what age did symptoms first appear?
If onset is in older age → consider dementia, stroke, Parkinson’s, epilepsy.
Are there neurological signs such as:

Unsteady gait, limb weakness
Slurred speech, facial droop
Seizures
Marked short-term memory impairment

Psychosis due to medical condition / substance / medication

Is there any medical illness affecting the brain (e.g., brain tumor, encephalitis, etc.)?
What medications are they using:

Dopaminergic agents (e.g., levodopa in Parkinson’s)
Illicit drugs / alcohol / stimulants

Do the onset and fluctuations of symptoms correlate with substance use?

2.2. Common assessment steps

In real clinical practice, doctors use a combination of:

History from the patient + from relatives (because the patient may not report everything)

Mental Status Examination (MSE)

Thought content: what other delusions are present?
Thought process: how organized/disorganized?
Perception: hallucinations?
Mood / affect
Insight & judgment

Physical and neurological examinations

Laboratory tests / brain imaging (if a medical cause is suspected)

CT/MRI brain
EEG (if epilepsy is suspected)
Blood tests for toxins/infections/metabolic problems

Ultimately, the clinician arrives at a primary diagnosis such as:

Schizophrenia with Frégoli delusion

Bipolar I disorder, current episode manic, with psychotic features (Frégoli-type misidentification)

Major neurocognitive disorder due to Alzheimer’s disease, with delusional misidentification (Frégoli type)

Psychotic disorder due to another medical condition, with Frégoli delusion

For writing purposes, the core idea is:

“Frégoli is a phenomenological pattern that sits within a primary disorder; it is not a standalone disease.”

Things that should also be assessed (in more detail)

When diagnosing, it is not enough to ask whether Frégoli is present or not;
one must also examine the risk context and overall functioning.

a) Level of insight

Simple questions include:

Does the patient accept that:

“What I’m thinking might not be 100% true”?

Or do they believe 100%, “without leaving room for the possibility of being wrong”?

Insight level influences:

Willingness to cooperate with treatment (e.g., taking medication)

Probability of arguments/confrontations with others

Whether CBT for psychosis can be used (a minimum level of insight is usually needed)

b) Risk to others / risk of violence

Points to evaluate:

Have they ever harmed anyone because they believed that person was “him in disguise”?

Have they ever carried weapons (knives, sticks, other tools), especially when going out?

Are there plans that sound concerning, e.g.:

“If he shows up again, I’ll make sure it ends once and for all.”

The more we see:

Frégoli theme + persecutory delusion + no insight
→ the more we need a clear safety plan (in some cases, hospitalization may be required).

c) Cognitive / neuro functioning

This is especially important when:

Onset is in older age

There is a history of brain injury / stroke / neurological disease

The clinician may order cognitive tests to examine:

How is short-term memory?

How is planning / multi-step task performance?

How is facial recognition / recognition of familiar people?

Sometimes, Frégoli may be the “tip of the iceberg” of dementia or secondary psychosis from brain disease.

d) Medications/substances

Some cases are caused by:

Use of dopamine agonists

Misuse of stimulants

Withdrawal from alcohol/benzodiazepines

If such a cause is identified, treatment involves adjusting/stopping the culprit medication + addressing substance use,
rather than labeling it as schizophrenia straight away.

4. Subtypes or Specifiers — Subtypes/specifiers (for academic writing)

There are no standardized specifiers like in DSM, but for systematic explanation (and to help make content more “premium”), Frégoli is often subdivided like this:

Pure Frégoli vs Mixed DMS

Pure: The Frégoli theme is predominant.
Mixed: Frégoli is found alongside Capgras / intermetamorphosis / subjective doubles in the same person. PMC+1

Primary (psychiatric) vs Secondary (neurological/medical)

Primary: Linked with schizophrenia spectrum or mood disorder with psychosis.
Secondary: Follows stroke, TBI, dementia, epilepsy, Parkinson’s/medications, etc. NCBI+2 PMC+2

Theme specifiers (content-based)

Persecutory Frégoli: “The same person is following / persecuting me.”
Erotomanic/Jealous overlay: Romantic/jealous/attachment themes layered on top (in some cases).
Systematized vs fragmented: The delusional story is well-structured vs fragmented (often depending on the primary disorder).

5. Brain & Neurobiology — Brain mechanisms / neurobiology

First, the big picture:
Most research sees Frégoli syndrome as a disturbance of “face-recognition networks + familiarity systems + reality-testing systems.”

Put simply:

The eyes see correctly,

The face-recognition system in the brain is too good / overactive (hyper-familiar),

But the “rational brake system” in the brain does not perform quality control → so the world is interpreted incorrectly.

5.1 Face recognition network & mis-tagged familiarity

In a typical person, when we see someone’s face, the brain uses a large network, not just a single spot:

Occipital lobe (visual cortex)
– Processes raw images: shapes, faces, light and shadow.

Fusiform gyrus / Fusiform Face Area (FFA)
– Key region linked to “face recognition.”
– Helps determine “this is a face” and “what kind of face / where have I seen it before.”
Many DMS review articles suggest that abnormalities in the fusiform gyrus and face-related networks contribute to delusional misidentification. PubMed+1

Anterior temporal lobe + Perirhinal cortex
– Link “faces” with “identity + meaning + experience.”
– Some studies suggest that underactivity of the perirhinal cortex → leads to feeling “unfamiliar” with familiar people (Capgras model).
Conversely, overactivity → explains hyperfamiliarity where strangers feel overly familiar, as if the brain is wrongly tagging them as “familiar.” PMC+1

Limbic system (amygdala, hippocampus, etc.)
– Adds “emotion” to faces: who we like or dislike, who is a threat, who is safe.
– If we have longstanding conflict with someone, the brain easily ties their face to “danger” or “anger.”

“Person identity nodes” (a concept in the DMS literature)
– Conceptually: nodes that encode “this is mother,” “this is an ex,” “this is the boss.”
– If the mapping “face → identity node” is distorted, many different faces may be incorrectly mapped to the same “person.” LWW Journals+1

The model often used for Frégoli is hyperfamiliarity + misbinding:

The brain generates a strong “this face is very familiar” signal, even though the person is a stranger.

Combined with misbinding to the wrong identity node → that familiarity is attributed to a single internal character (e.g., an enemy or stalker).

The result at the perceptual level:

Ten strangers = the same person in many forms.

Research on hyperfamiliarity for faces (HFF) shows cases where people feel familiar with many faces, but it does not become a delusion if frontal control is intact and they have insight like “My brain is probably acting weird.” ScienceDirect+1

Frégoli = HFF + a broken belief system → turning a “strange feeling” into a fixed delusional belief.

5.2 Right hemisphere & frontal lobe — The broken rational “brake”

The group of Delusional Misidentification Syndromes (DMS) (including Capgras, Frégoli, intermetamorphosis, etc.) is often found after brain lesions, especially involving the right hemisphere + bifrontal regions. Ovid+1

Evidence includes:

Cases after right-sided stroke, hemorrhage, or tumor

Cases with atrophy or lesions in the right frontal lobe, right temporal lobe, and parietal regions

Neuroimaging showing abnormal connections in right temporal–frontal networks, etc. PubMed+1

The frontal lobe (especially the right side) has major functions directly related to delusions:

Reality monitoring / belief evaluation

Checks whether “what the brain proposes” makes sense.
Acts like QA: unusual thoughts/feelings must pass this checkpoint before turning into stable beliefs.

Executive function / cognitive control

Shifting perspectives, entertaining alternative scenarios, updating beliefs when confronted with new evidence.
If this system fails → old beliefs become rigid (fixed beliefs).

Attentional control / suppression of noise

Filters out unimportant information.
If impaired → everything appears “significant,” opening the door to over-interpretation and random connections.

The “two-factor theory” used to explain monothematic delusions (including Frégoli) states: ResearchGate+1

Factor 1: An abnormal experience (e.g., hyperfamiliarity, a face that “feels like it must be him”).

Factor 2: A defective belief-evaluation system (frontal) → failing to reject that idea.

In ordinary people:

Feeling that a stranger looks familiar →
“Wow, they look like my old friend.”

The frontal QA says, “There’s not enough evidence; let’s keep this as just a feeling.”

In people with Frégoli:

They feel hyperfamiliarity →
“This is definitely him in disguise.”

Frontal QA fails → does not discard the thought; instead, it builds a supporting narrative around it.

5.3 Limbic / Insula / Temporal–Frontal networks — “Tagging faces as threats”

Many cases, especially after stroke or brain lesions, show abnormalities across broad networks, including:
insula, temporal, frontal, and limbic areas. LWW Journals+1

Functionally:

Amygdala & limbic system

Detect threat, fear, and salience.
If an individual has long been tagged as a danger, even slightly similar cues can trigger a strong alarm.

Insula

Related to interoception (awareness of bodily states) and emotional salience.
If hyperactive → can produce intense feelings of being “on edge / creeped out / uneasy” without any clear external reason.

Temporal–frontal connections

Link “identity recognition” from the temporal lobe with “interpretation + planning responses” in the frontal lobe.
If this pathway is miswired / the network is imbalanced → the external world is repeatedly interpreted as a threat from “the same person.”

Peter Gerrans has suggested that hyperfamiliarity in DMS is like a misfiring signal that something is odd (surprisal), and the default mode network (DMN) then constructs a narrative around it, such as:

“Why do I feel so familiar with this person when I’ve never seen them before?
Ah… because it’s the same person in disguise!” Frontiers

This is a normal function of the brain — but in delusional cases, it creates a story and then believes it 100%.

5.4 Comparing Capgras vs Frégoli at the brain level (for a clear framework)

Point of comparison	Capgras	Frégoli
Main experience	“A familiar person seems not to be the real person” (hypo-familiarity)	“A stranger seems to be the same familiar person” (hyper-familiarity)
What is believed to be happening	Loved one has been replaced / is an impostor	An enemy/familiar person disguises themselves as many different people
Proposed mechanism	Decreased emotional familiarity signal toward familiar faces	Excessive familiarity signal toward strangers’ faces
Shared brain factors	Abnormalities in face-recognition + limbic + right frontal networks	Similar, but with emphasis on hyperfamiliarity + failure of belief evaluation

Neuroimaging and neuropsychology studies suggest that the DMS group shares a common problem: distortion of “affective familiarity” plus abnormal belief evaluation. The direction of the familiarity disturbance (too much / too little) and the precise narrative differ by subtype. PubMed+2 boris-portal.unibe.ch+2

5.5 Summary as a “brain step-by-step” model of how Frégoli misfires

Imagine a patient walking in a mall and seeing a stranger:

Visual & face processing

Occipital + fusiform areas receive the facial image → they are functioning.

Familiarity signal mis-tuned (hyperfamiliarity)

The perirhinal/temporal network fires a signal:

“This face is extremely familiar!” (even though the person has never been seen before) PMC+1

Limbic & salience networks add emotion

Amygdala/insula link this familiarity to the memory of “that threatening person.”
The body feels tense; heart rate increases.

Frontal belief system fails (right frontal / bifrontal dysfunction)

Normally, there would be an inner voice: “Maybe I’m just imagining it; maybe they only look similar.”
But the brake is broken → the conclusion becomes:

“This is definitely him in disguise.”

DMN builds a supporting story

“See? He keeps walking past the store I like.”
“Last time there was someone dressed similarly.”
Every new event is drawn in to confirm the existing story → the delusion grows stronger. Frontiers+1

This is the neuropsychological loop that explains both the subjective experience and overt behavior of someone with Frégoli syndrome.

6. Causes & Risk Factors

For this topic, if you want the article to look “smart but easy to understand,” think of:

Frégoli = a type of delusional “software”
running on diverse “hardware” or primary disorders.

It is not a standalone disease, but rather an end-point phenomenon that can arise from:

Psychiatric disorders (primary psychosis / mood disorders)

Brain diseases (neurological / neurocognitive)

Medications/substances

Psychological and environmental amplifiers

6.1 Psychiatric causes — Psychiatric disorders that often include Frégoli

1) Schizophrenia spectrum & other psychotic disorders

Frégoli is frequently found in the context of:

Schizophrenia

Schizoaffective disorder

Delusional disorder (especially persecutory type)

In this group, DMS often co-occurs with:

Multiple delusional themes (persecutory, referential, grandiose, etc.)

Hallucinations

Disorganized thinking/behavior

Reviews on misidentification syndromes note that a substantial portion of Fregoli cases are based primarily on psychotic disorders, with strong persecutory content, such as the belief that the follower changes faces/disguises to approach them in many places. Cleveland Clinic+1

2) Bipolar disorder with psychotic features

There are reports of Capgras + Frégoli in bipolar patients with psychosis who improved after receiving a long-acting antipsychotic.

In mania or severe depression with psychosis, thought speed increases, sleep is reduced, and the person over-attributes meaning to events → making misidentification-type delusions more likely. ResearchGate+1

3) Other groups

Major depressive disorder with psychotic features (less common than in schizophrenia/bipolar)

Schizophreniform / brief psychotic disorder (few case reports, but theoretically possible)

Overall psychiatric picture:

If psychotic symptoms begin in adolescence/young adulthood, and there is a prior history of psychosis → clinicians generally think “primary psychiatric” first.

Frégoli in this group usually appears with other delusional themes and clear social-functional impairment.

6.2 Neurological / Neurocognitive causes — Brain disorders that can produce Frégoli

A 2025 narrative review on misidentification syndromes points out that many DMS cases (including Frégoli) have underlying brain diseases, especially right-hemisphere lesions such as stroke, tumor, or trauma. LWW Journals+1

Main categories:

1) Stroke (ischemic / hemorrhagic)

Especially strokes affecting:

Right frontal lobe

Right temporal lobe

Parietal lobe

Or the temporal–frontal network

Post-stroke Fregoli cases often present with:

Delusional misidentification

Combined with impairments in visuospatial skills, attention, and executive function. PubMed+2 Karger Publishers+2

Clinical clues:

Frégoli-type delusions begin clearly after a stroke.

There may be hemiparesis/weakness, dysarthria, and gait disturbances.

2) Traumatic Brain Injury (TBI)

Blunt head trauma / brain injury, especially to frontal / right temporal regions, can lead to DMS.

Post-TBI, one may see:

Memory problems
Personality change
Impulsivity + poor emotional regulation

— a combination that raises the risk of misidentification delusions. LWW Journals+1

3) Dementia / Neurodegenerative disorders

Especially:

Alzheimer’s disease
Lewy body dementia
Frontotemporal dementia

When neurodegeneration reaches:

Temporal regions (face/identity recognition)
Parietal-visual areas
Frontal regions (judgment/insight)

→ delusional misidentification patterns can easily emerge.

In dementia, Capgras is more common than Frégoli, but Frégoli has also been reported. LWW Journals+1

4) Epilepsy

Especially epilepsy with a temporal lobe focus.

There are cases reporting hyperfamiliarity for faces (HFF) associated with seizure activity and left-side lesions, etc., but HFF often does not become delusional when insight is preserved. ScienceDirect+1

When epilepsy co-occurs with frontal/network abnormalities, DMS can fully develop.

5) Brain tumors / developmental anomalies / other CNS diseases

Fregoli has been reported in association with brain tumors, developmental anomalies, or non-specific structural abnormalities, although such cases are rare.

What they have in common is that they affect the network of “face recognition + familiarity + frontal control,” creating conditions for similar mechanisms to arise. CRCP+1

Neurological summary:

If Frégoli symptoms begin in older age, with neurological signs and a history of stroke/TBI/epilepsy/brain disease → clinicians must suspect a brain-based cause first, rather than assuming “pure psychiatric illness.”

6.3 Substance / Medication-related — Drugs and substances linked to Frégoli

This category must never be forgotten when encountering Frégoli:
certain medications/substances can trigger psychosis + misidentification.

1) Dopaminergic medications in Parkinson’s disease

Parkinson’s patients use levodopa, dopamine agonists to increase dopamine.

Dopamine surplus in certain regions + pre-existing vulnerability → may cause hallucinations and delusions.

A 2025 case report described a PD patient given 24-hour levodopa infusion who developed auditory hallucinations + persecutory delusions + a Frégoli theme. PMC+2 neuroscijournal.com+2

Older literature also consistently states that dopaminergic medications are a major factor in psychosis in PD, though not all patients are affected. ijanm.com+1

In PD patients who develop Frégoli-type delusions, clinicians must consider:

Medication (dose, timing)

Progression of dementia in PD

Other precipitating factors (sleep, infection, metabolic disturbances)

2) Alcohol / drugs / other substances

Some Fregoli cases have been reported in the context of alcohol use, illicit drug use, or withdrawal, although prevalence numbers are unclear due to reliance on case reports. CRCP+1

Stimulants, high-potency cannabis, hallucinogens, etc., can induce psychosis + paranoia in vulnerable individuals.
If such substances act on a brain already prone to abnormal familiarity networks → the Frégoli pattern can emerge.

Key idea:
When evaluating Frégoli, one must always ask about medications/substances:

What medications are you taking? When did you start/increase/change them?
Do you use illicit drugs or alcohol?

6.4 Risk amplifiers — Not primary causes, but factors that make the fire easy to ignite

These are the “fuel around the bonfire”:

1) Sleep deprivation & severe stress

Lack of sleep → frontal control drops, emotion regulation collapses.

Chronic severe stress → HPA axis overactivation, mood instability, increased paranoid thinking.

In people with pre-existing brain vulnerability (e.g., schizophrenia, brain lesions), sleep deprivation/stress can trigger a rapid intensification of delusional content.

2) Personality traits: paranoid / suspicious style

People with patterns like:

Easily suspicious of others

Highly sensitive to betrayal

Frequently believing conspiracy theories

When they experience poorly explained hyperfamiliarity, they are more likely to “choose” a narrative of persecution/chasing than others → making a persecutory Frégoli theme more likely. LWW Journals+1

3) History of trauma / stalking / past violence

If someone has actually been followed, assaulted, or stalked in the past,
their brain becomes sensitive to cues suggesting “he’s back.”

When hyperfamiliarity is layered onto background trauma → the “he’s following me” narrative can feel very plausible.

4) Social isolation & cognitive echo chambers

Social withdrawal → lack of external feedback from others saying “Hmm, maybe this isn’t true.”

Living in an environment saturated with news, conspiracy content, shapeshifter/surveillance stories, etc. →
provides a ready-made set of explanations when strange feelings of familiarity arise.

When hyperfamiliarity appears, the brain already has a narrative “ready to serve”:

“There — he’s a spy in disguise, hunting me down.”

6.5 Overall pathway: from vulnerability → triggers → Frégoli

For a visual article (e.g., a pathway diagram), you can summarize:

Vulnerability (baseline vulnerability)

Brain diseases (stroke, TBI, dementia, epilepsy, PD, etc.)
Psychiatric disorders (schizophrenia, bipolar with psychosis, etc.)
Structural anomalies / developmental disorders LWW Journals+1

Neurobiological mechanism

Hyperfamiliarity signals from temporal/perirhinal/face-recognition networks
Frontal (right/anterior) dysfunction → failed belief evaluation
Limbic/insula hyper-salience → interpreting everything as a threat PMC+2 Ovid+2

Triggers

Medications (dopaminergic), substances
Sleep deprivation, severe stress, trauma reactivation PMC+2 ijanm.com+2

Psychological & social context

Paranoid personality style
Social isolation, lack of feedback
Consumption of content that supports “pursuit/conspiracy” narratives

Phenomenology = Frégoli syndrome

Many strangers → believed to be “one person in multiple bodies.”
Main themes: persecution, spying, pursuit.

7. Treatment & Management — Treatment and management

There is no “one-size-fits-all recipe,” because management must treat the underlying disorder + manage risk as a pair (it is more like incident management than treating a single symptom).

1) Treat the underlying condition (First principle)

If secondary: manage stroke/TBI/seizure/delirium/dementia and adjust medications.

If psychiatric: follow guidelines for the primary disorder (schizophrenia/bipolar/delusional disorder). NCBI+1

2) Pharmacotherapy (the main clinical pillar)

Antipsychotics are typically first-line to reduce delusions/suspicion/agitation.

If there are bipolar mood swings: consider mood stabilizers according to the primary disorder.

Some cases improve with long-acting injectable antipsychotics (per case reports). PMC

3) Psychosocial / behavioral management

Risk assessment & safety planning: essential if there is a persecutory theme (to prevent confrontations and misinterpretation).

Communication that does not directly attack the delusion (avoid head-on confrontation), but instead uses emotional validation and guides the patient back toward safety.

When symptoms are more stable: CBT for psychosis with gradual reality-testing can be used in some patients who have begun to develop insight.

4) Environmental & systems-level interventions (very practically helpful)

Reduce triggers (news/social media/overexposure to crowds).

Establish consistent sleep routines.

Provide family education so that relatives respond in a structured manner and do not unintentionally fuel the delusional storyline.

8. Notes — Points to know (for sharp and safe writing)

Frégoli ≠ just misrecognizing faces.
It is a belief that cannot be corrected by reasoning/inhibition and thus becomes a delusion. NCBI+1

It must be distinguished from other DMS conditions:

Capgras: A loved one is believed to be replaced by an impostor.
Intermetamorphosis: People are believed to exchange identities.
Subjective doubles: The person believes they have “another self” or double, etc. NCBI+1

Safety risk is a major issue

Persecutory theme + belief that “the same enemy is in disguise” → risk of confrontation/violence/repeated police reports/running away from home.
In writing, highlighting a dedicated “risk & safety” section makes the piece look very professional. PMC+1

If symptoms begin suddenly in an older person, always think of brain causes first:

Stroke/delirium/dementia/medication effects are priorities. NCBI+1

Read Schizophrenia

References — Frégoli syndrome / Delusional Misidentification

Bashir S, Grover S.
Delusional Misidentification Syndrome. StatPearls [Internet]. NCBI Bookshelf; 2024. ncbi.nlm.nih.gov

Kochuparackal T, et al.
A “Contemporary” Case of Frégoli Syndrome. Prim Care Companion CNS Disord. 2012. Case report of a schizophrenia patient with Frégoli in a modern social media context. PMC

Ogata S, et al.
A case of Frégoli syndrome following 24-hour levodopa-carbidopa intestinal gel infusion in a patient with Parkinson's disease undergoing STN-DBS. Clin Parkinsonism Relat Disord. 2025. PD + levodopa + DBS leading to Frégoli. PMC+1

Grover S, et al.
Misidentification syndrome: A narrative review. Indian J Psychiatry (International Journal of Psychiatry in Clinical Practice / INPJ). 2025. Large narrative review on DMS (including Capgras / Frégoli). Lippincott Journals

Ghannadi F, et al.
Fregoli Delusion. Clinical case report of a 23-year-old male with Fregoli, trauma history, and developmental anomalies. crcp.tums.ac.ir+1

Teixeira Dias et al.
Neuropsychiatric Features of Fregoli Syndrome: An Updated Review. (Neuropsychiatry / J Neuropsychiatry Clin Neurosci.) Focus on neuropsychiatric features of Frégoli and other DMS. Psychiatry Online+1

Anderson CA, et al.
Delusional Misidentification Syndromes: Progress and Pitfalls. J Neuropsychiatry Clin Neurosci. 2016. Important review on DMS (Capgras, Frégoli, erotomania, etc.). Psychiatry Online

Salviati M, et al.
Fregoli syndrome in course of infection-related delirium. A case report. Psychopathology. 2014. Frégoli triggered by delirium due to acute infection. Journal of Psychopathology

Kumar PNS, et al.
Fregoli syndrome in schizophrenia: about a case report. Asian Pac Psychiatry / Asian Journal of Psychiatry. 2018. Frégoli in a schizophrenia patient. ScienceDirect

Stewart JT.
Frégoli syndrome associated with levodopa treatment. Mov Disord. 2008. Early case linking Frégoli to levodopa in Parkinson’s disease. Movement Disorders+1

Gower G, et al.
Delusional Misidentification Syndromes: a patient level meta-analysis of 422 cases. J Neurol Neurosurg Psychiatry. 2025 (suppl.). Meta-analysis of many DMS cases, clinically and neuroanatomically. JNNP

Le Monde – Réalités Biomédicales.
Syndrome de Fregoli: la conviction délirante qu'un proche se déguise en d'autres personnes. 2025. French-language article summarizing Frégoli cases and research; a good popular reference. Le Monde.fr

Wikipedia – Fregoli delusion.
Used as an overview + gateway to primary literature on neurobiology, levodopa, TBI, etc. (should not be the sole primary reference). Wikipedia

Fregoli syndrome, Fregoli delusion, delusional misidentification, delusional misidentification syndromes, DMS, misidentification delusion, positive doubles, hyperfamiliarity, face recognition network, fusiform gyrus, temporal lobe, right frontal lobe, right hemisphere lesion, executive dysfunction, belief evaluation, persecutory delusion, paranoia, schizophrenia spectrum, schizophrenia with Fregoli delusion, bipolar disorder with psychosis, dementia with delusions, vascular dementia, stroke-related psychosis, traumatic brain injury, TBI, Parkinson’s disease psychosis, levodopa-induced psychosis, dopaminergic medication, psychosis due to medical condition, organic psychosis, Capgras vs Fregoli, Capgras syndrome, intermetamorphosis, subjective doubles, delusional false recognition, neuropsychiatry, cognitive neuropsychiatry, risk assessment, violence risk, antipsychotic treatment, long-acting antipsychotic, CBT for psychosis, brain lesions, right temporal lesion, neuroimaging, case report, rare psychotic syndrome

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