Somatic Delusions

1. Overview — What Are Somatic Delusions?

Somatic delusion is a “false belief about one’s own body” that is so deeply fixed it is almost immovable, even when medical tests are normal or multiple doctors consistently confirm that the body does not have the problem the person believes it has. The key point is that it’s not just “worrying too much about health,” but believing at the level of reality (as if it were a fact) that one’s body/organs/odor/appearance “definitely have some kind of damage or abnormality.”

The content of somatic delusions usually revolves around the body/organs/bodily functions/bodily sensations/appearance, and sometimes includes smell. For example: believing that the intestines are rotten inside, that worms or insects are crawling under the skin, that fibers or threads are emerging from the skin, that the blood has turned toxic, that the brain is melting, or that one’s body odor is so strong and foul that people around are disgusted—even though others do not notice anything, and medical examination does not find the abnormalities they describe.

What makes it a “delusion” is not how bizarre the content sounds, but that the person is 100% confident in this idea and refuses to change it even in the face of a large amount of contradictory evidence—such as X-rays, MRI scans, blood tests, and evaluations by multiple specialists. Put simply, when they talk about it, they are not speaking in the tone of “I’m afraid I might have…”, but in the tone of “This is what I already have; it’s just that no one is willing to acknowledge the truth.”

Very important: Somatic delusion is a “delusional theme,” not a standalone disease name. It can appear in several disorders, such as:

Delusional Disorder, somatic type

Schizophrenia / Schizoaffective disorder

Mood disorder with psychotic features (e.g., major depression with psychotic features)

Substance/Medication-induced psychotic disorder (from certain drugs/stimulants)

Psychotic disorder due to another medical condition (arising from bodily illness that affects the brain)

Therefore, when we say “somatic delusion,” we are referring to “false bodily content of belief,” not automatically naming a specific disorder. One must always consider the overall clinical picture and other symptoms to see whether it fits into the schizophrenia spectrum, mood disorders, or secondary psychosis from medical conditions/substances.

Another commonly misunderstood point is that somatic delusion is not lying, and it is not “faking illness” to get attention. People with somatic delusions truly believe that the problem is happening in their body. Trying to tell them “you’re overthinking,” “you’re imagining it,” or “you’re mentally weak” usually doesn’t help; it can even increase their sense of isolation, invalidation, and strengthen their attachment to the belief.

Compared to Somatic Symptom Disorder / Illness Anxiety Disorder, the crucial difference is the level of conviction and flexibility. Someone with health anxiety might say, “I’m afraid I might have cancer,” and if they receive good explanations and thorough tests, some people may be able to relax at least somewhat. In somatic delusion, the tone becomes, “I definitely have cancer, but no one is telling me the truth,” and new information is rarely used to reduce the belief.

Somatic delusions can also be deeply tied to personal emotion and meaning. For example, someone with severe depression might have themes like “my body is rotting, my blood is poisonous, my organs have stopped working,” accompanied by feelings of worthlessness, hopelessness, and wanting to disappear from the world. In some cases, this can come close to a Cotard-like picture (“I am dead, my organs are rotting inside”).

In terms of daily functioning, a person with somatic delusions does not always have to look “completely bizarre.” Especially within the framework of Delusional Disorder, somatic type, many patients can hold coherent conversations, work, take care of themselves, and live normally in most areas—except for “one small world” that revolves around their own body. In that inner world, the rules and “facts” may be completely different from those of other people.

What follows somatic delusion is usually not just the belief itself, but repetitive behaviors driven by that belief—for example, seeing many doctors (doctor shopping), asking for repeated blood tests/scans/examinations, picking/scratching/puncturing the skin to “get something out,” vigorously washing or overusing chemicals on the skin, and isolating from society out of shame, believing they are “disgusting/deformed/dangerous to others.” These behaviors further worsen quality of life, and in many cases may actually create wounds or physical illnesses that started from the false belief.

Overall, Somatic delusions = the brain “constructing a misdirected narrative” to explain bodily signals—which may be real, not real, minor but magnified, or caused by actual illness—but the interpretation leaps too far, becomes rigid, and is shielded so that external evidence can hardly get through. The result is a complex mixture of suffering in body + mind + social life, which requires thorough assessment of medical conditions, psychiatric evaluation, and long-term multidisciplinary care—not just saying “you’re imagining it” and leaving it there.

2. Core Symptoms — Core Features of Somatic Delusions

When we talk about somatic delusions, there are 3 major cores that we need to understand clearly:

A: False bodily belief content

B: Behaviors that follow from that belief

C: Other domains of functioning that may still appear “intact”

A) False bodily beliefs that are “fixed and persistent”

The heart of somatic delusion is “being 100% convinced that there is something wrong with one’s own body,” while:

Medical evidence, test results, scans, blood tests, etc.
→ do not support that belief at all

Yet the person does not change the belief, or it is extremely hard to change, even when several doctors repeatedly confirm the same thing.

1. Core elements of the belief (Delusional content)

Common themes include:

Believing there is a living organism underneath the skin

Delusional infestation / parasitosis
“It feels like something is crawling and burrowing inside me all the time.”
Some may scratch with their nails, poke with needles, or squeeze with tweezers to “get it out.”

Believing that fibers/threads/plastic fragments are coming out of the skin

Often referred to as Morgellons (in psychiatric frameworks generally considered a subtype of delusional infestation)
The person might collect lint, dust, or debris in a container to show the doctor and say, “Here, these are fibers from my body.”

Believing internal organs are damaged/rotting/not functioning

For example, “All my kidneys are destroyed,” “My intestines are rotten and decaying from the inside,” “My brain is melting,” “My blood has become poisonous.”
This is despite normal physical exam and investigations, or only minor abnormalities that are interpreted by the person as catastrophically severe.

Believing their body emits a very strong, foul odor

Some are convinced they “smell so bad that people around can’t stand it.”
Even though others say they don’t smell anything, and medical evaluation finds no abnormality.

What makes this a delusion is not merely that “the content is strange,” but that:

The level of conviction = treated as an unquestionable “fact.”

Very low flexibility = contradictory evidence, alternative explanations, don’t really sink in.

It becomes tightly linked to identity = “This is definitely what I am,” “My body really is ruined.”

2. Bodily sensations + misinterpretation

Many cases do not start from “pure imagination,”
but from some “bodily sensations,” such as:

Itching / tingling / numbness / warmth / tightness

Fullness / unusual pain / weird tingling under the skin / shooting or stabbing sensations

Normally, our brain interprets these fairly neutrally, e.g.,
“It might be a mild allergy / muscle tension / poor circulation / stress-related stomach pain,” etc.

But in somatic delusion, the brain jumps to an “extreme” interpretation:

“This kind of itch = there must be worms underneath.”

“Chest tightness = my heart has stopped working already; no doctor understands.”

“Sharp pains in my head = my brain is slowly rotting.”

The key point is that the interpretation is not just “worry,” but a belief at the level of fact (“It is already happening”).

And in some people, there are perceptions that qualify as hallucinations alongside the delusion, such as:

Feeling tiny creatures crawling (tactile hallucination)

Smelling a foul odor from oneself while others do not (olfactory hallucination)

But even if there are no hallucinations at all, a rigid interpretation alone can still fit within somatic delusion.

3. Emotions that accompany the belief

Somatic delusion is not a “neutral” belief; it usually comes with:

Very high anxiety

Fear of death/disability

Shame—especially if they believe they smell bad or their appearance is deformed

A sense that doctors/others “don’t understand,” “aren’t being honest”

These emotions create genuine suffering for the person, which makes the false belief even more deeply entrenched, because it feels “important” and carries heavy emotional weight.

B) Behaviors driven by the belief (safety behaviors) that form loops

When the brain is 100% convinced that “my body has a serious problem,”
the automatic behavioral response is to try to fix/protect/check to make sure it’s safe.

These behaviors are collectively called safety behaviors = actions done to “feel safer,”
but in the long term they actually strengthen the delusional belief, because every time they are performed → the brain gets the message that:

“If I don’t do this = it’s truly dangerous.”
That means this matter is truly serious → the delusion becomes stronger.

1. Repeated body checking

Examples:

Staring in the mirror for long periods, many times a day; taking photos of a lesion and zooming in and comparing

Repeatedly feeling the same body part to check for lumps/changes

Using tools to poke/scratch/squeeze/pry at the skin to “prove” or “get something out”

Negative consequences:

Skin/tissues become injured → more pain/itch/inflammation → more “evidence” for the delusion

Enormous time spent each day → disrupts sleep, work, and social life

2. Doctor shopping / investigation seeking

Visiting many doctors across multiple specialties

Requesting repeated CT, MRI, blood tests, X-rays, endoscopy, etc.

When results are normal → this does not ease anxiety, but is interpreted instead as:

“The equipment isn’t sensitive enough / the doctor isn’t good.”
“The doctor is lying/hiding something / the medical system is not telling the truth.”

This loop causes:

Waste of resources, time, money

The belief becomes more “bulletproof,” because now there is a narrative:

“I really am sick, but no one is willing to acknowledge it.”

3. Over-washing/scrubbing/treating

Especially when the person believes there are foreign bodies/contaminants/germs/odor:

Vigorously scrubbing the body frequently, using very strong soaps or cleaning agents

Using chemicals that should not be applied to skin

Taking or applying medication beyond medical advice

Using tools/sharp objects to “remove something”

The result:

Damaged skin, abrasions, infection

But paradoxically, the new wounds become “evidence” for the delusion:
→ “See? My skin really is abnormal.”

4. Endless reassurance seeking

Asking others: “Can you smell it?”, “Does this wound look scary?”, “Does my face look crooked?”

Reading information online late into the night, searching for diseases that might match

At first, reassurance may reduce anxiety “a little,”

But soon the doubt/fear returns → they ask again → the loop continues

This type of reassurance seeking differs from “ordinary stress” in that:

The reassurance given does not “stick” very well

The brain barely uses new information to update the belief

Eventually, people around them become tired/annoyed → the patient feels even more isolated and even more convinced that “no one understands.”

5. Avoidance of social situations

Because they believe they “smell bad / are deformed / have something dangerous inside,” patients often:

Avoid being physically close to others (sitting far away, not taking public transport, not using meeting rooms)

Decline activities that require closeness, such as eating with friends, attending social events

In cases where they believe they are contagious/a source of infection → they feel intense guilt and isolate themselves further

Consequences:

Relationships are damaged

Work/study is affected

The cognitive loop “I’m different / I truly have a problem” becomes stronger

C) Other domains of functioning can look “normal” (especially in Delusional Disorder)

This point is crucial for understanding Delusional Disorder, somatic type:

Many patients can:

Hold coherent conversations

Reason normally in other topics

Work and take care of themselves

Do not show disorganized speech, grossly disorganized behavior, or the negative symptoms typical of schizophrenia

“Almost all the pathology is wrapped into a single theme”:
that is, issues concerning body/organs/odor/appearance, which become a separate internal world.

As a result:

Some people around them may think, “They’re normal, really—just weird on that one topic.”

This can delay diagnosis, because they don’t look “psychotic” in the more obvious way that schizophrenia does, with multiple domains clearly affected.

But clinically, just having one fixed, deeply entrenched delusion centered on a single theme can be enough to qualify for Delusional Disorder (if other criteria are met).

3. Diagnostic Criteria — Practical Diagnostic Perspective

This section explains three levels:

When we encounter “somatic delusion” as a symptom (symptom-level)

When it meets criteria for Delusional Disorder, somatic type (disorder-level)

What other conditions “look similar” and should be differentiated (differential diagnosis)

Note: The main references are DSM-5-TR and modern clinical concepts, but the explanation here uses accessible clinical language rather than verbatim manual text.

3.1 Somatic delusion as a symptom (Symptom-level)

Question: “When do we call it a somatic delusion rather than just health worry?”

A simple way is to look at these 5 dimensions:

Content of belief about the body

There is a clear theme related to organs, bodily function, appearance, odor, or foreign bodies inside.

Level of conviction

It’s at the level of “This is certainly true,” not just “I’m afraid it might be…”
Spoken in a factual tone, such as “I smell really bad,” not just “I’m worried I might smell bad.”

Resistance to contradictory evidence

Tests are normal, multiple doctors say results are normal, and medical mechanisms are explained → but the belief hardly shifts.
Some even reinterpret: “Doctors are hiding something,” “The equipment isn’t good,” “No one is telling me the truth.”

Impact on behavior / daily life

The safety behaviors described above appear: repeated checking, picking, seeing many doctors, vigorous washing, social withdrawal.
There is clear impact on work/study/relationships.

Insight about their own thoughts

Ask: “Is it possible that things might not be exactly as you think, 100% of the time?”
If the answer is: “No, that’s impossible” → closer to delusion.
If the answer is more like: “I’m not sure, but I’m very scared” → more likely in the zone of somatic symptoms/illness anxiety rather than full delusion.

If these 5 dimensions are clearly on the delusional side, then we consider that the person has a somatic delusion as a symptom.
Which disorder it belongs to (schizophrenia, delusional disorder, mood disorder with psychotic features, etc.) depends on the full case picture.

3.2 When it “becomes a disorder”: Delusional Disorder (Somatic Type)

Delusional Disorder has key criteria (summarized, not verbatim DSM but identical in meaning) as follows:

There is one or more delusions for at least 1 month.

Not limited to somatic content, but for somatic type the focus is the body.

The delusion must be “persistent,” not a momentary mood-related idea.

The person has never met full criteria for schizophrenia.

Meaning they do not prominently exhibit:

Severe disorganized speech
Obvious disorganized or catatonic behavior
Full negative symptom syndrome (flattened affect, avolition, etc.)

Hallucinations may be present to some degree, but they must not be more pervasive than is typical of schizophrenia.

Overall functioning is not as severely impaired as in schizophrenia.

The person can still:

Work
Take care of themselves
Speak coherently in other areas

Impairment is usually limited to the area the delusion touches—for example, certain aspects of work, specific relationships.

If mood episodes (e.g., major depression, mania) are present,

Their duration/salience must be “less than” that of the delusional periods.
If mood symptoms dominate, the diagnosis leans more toward mood disorder with psychotic features.

The disturbance is not attributable to substances/medical conditions.

One must actively screen for causes such as substance use, medications, medical illnesses, tumors, neurological disorders, etc.
If a medical illness can “directly account” for the psychosis → it is diagnosed as psychotic disorder due to another medical condition instead.

So what makes it “somatic type”?

The majority of delusional content concerns the body—for example:

Body odor, appearance, deformed organs, foreign bodies, insects, fibers, tissue rot, etc.

If there are multiple themes (e.g., somatic + persecutory + jealousy) and none is clearly dominant → it may be classified as mixed type instead.

3.3 What needs to be clearly differentiated — Differential Diagnosis

Many disorders/conditions involve “concern about the body,” but are not somatic delusions.
This is crucial both for treatment and for explaining things to readers.

1. Somatic delusion vs Somatic Symptom Disorder / Illness Anxiety Disorder

Similarities:

Both feature worry about health/bodily symptoms.

Both may involve frequent doctor visits, body focus, repeated symptom checking.

Differences:

Level of conviction

Illness Anxiety / Somatic Symptom:

“I’m afraid I might have cancer.”
When given good medical explanations → some can indeed feel less anxious.
Language uses “might, I’m afraid that, I worry that…”

Somatic delusion:

“I definitely have cancer, doctors just refuse to tell me.”
Evidence does not shift the belief.
The belief is held as a “fact.”

Attitude toward alternative explanations

Illness Anxiety: They can still think, “Maybe it’s related to stress, but I’m very worried.”
Delusion: They often reject other explanations rigidly.

Facial expression/tone when narrating

Illness anxiety: full of questions, doubt, hesitation.
Somatic delusion: spoken as if stating facts → “This is how it is, for sure.”

2. Somatic delusion vs Body Dysmorphic Disorder (BDD)

BDD is a condition where a person is preoccupied with perceived “flaws” in appearance, real or imagined, such as:

“My nose is so crooked everyone must notice,” “My skin is a mess,” “My face is deformed.”

In DSM-5 there is a specifier for insight level:

Good/fair insight: they recognize the thought may be exaggerated.

Poor insight: they believe it quite strongly.

Absent insight/delusional beliefs: they believe it at a delusional level.

Therefore, BDD (with delusional beliefs) and somatic delusion involving appearance
technically overlap significantly, and in practice clinicians consider:

Longstanding history of appearance-related preoccupation

Behaviors such as prolonged mirror checking, camouflaging with makeup, repeated requests for cosmetic surgery

The overall pattern: “Is this BDD with very poor insight?” or “Is this Delusional Disorder, somatic type?”

For writing a blog explanation, it’s fine to say:

In cases where the focus on appearance is extremely narrow and the behaviors look like BDD,
the condition is often categorized as BDD (with delusional beliefs) rather than using the Delusional Disorder label directly,
but the level of conviction is effectively the same as a delusion.

3. Somatic delusion vs OCD

In OCD, patients often have:

Obsessions → e.g., “If I think this, it means I’m a bad person,” “If even a tiny amount of contamination remains, others might die because of me.”

Compulsions → washing, checking doors, counting, etc., to relieve anxiety.

Key difference:

OCD typically has a sense that the strange thoughts are “not consistent with self” (ego-dystonic)

“I know this sounds irrational, but I can’t stop thinking it.”

Somatic delusion tends to be ego-syntonic

“It’s not irrational; it’s the truth about me.”

Even though in some cases OCD insight is very low, appearing “almost delusional,”
a clear history of classic OCD patterns (recurrent intrusive thoughts/rituals) helps distinguish it.

4. Somatic delusion vs Psychosis due to Medical Condition / Substance-induced

This is the most dangerous one to miss, because:

Some physical/neurological conditions—such as brain tumors, certain epilepsies, endocrine disorders, brain infections, etc.—
→ can produce psychosis + altered bodily perception.

Clues that help differentiate:

Age of onset: If psychosis starts at an older age than is typical for primary psychosis → we should suspect medical causes more strongly.

Associated neurological symptoms: Numbness, unilateral weakness, seizures, gait disturbance, memory loss, etc.

Relationship with substance/medication:

Did the delusion appear while using or withdrawing from a substance?
Any history of stimulants, hallucinogens, or high-dose medications?

If these clues are present → the approach is to treat it as secondary psychosis first, and then only label primary psychosis after excluding medical/substance causes.

4. Subtypes or Specifiers

A) Within the framework of Delusional Disorder (DSM-style subtypes)

Somatic type: Main theme is body/health/appearance.

Mixed type: Multiple themes, with none clearly dominant.

Unspecified type: Theme cannot be clearly categorized.

There are teaching/clinical summary documents (e.g., University of Utah Health – Physicians) that outline these subtypes (including mixed/unspecified) used in practice.

B) Specifiers often used clinically (even if not all are official subtype labels)

Insight level (good–poor–absent): Very important in BDD/OCD-related cases and helps guide treatment (American Psychiatric Association).

Presence of bodily/tactile hallucinations or not: In delusional infestation, tactile hallucinations are not uncommon (Psychiatrist.com).

Stable vs fluctuating by mood/substance/medical illness: Helps differentiate primary vs secondary delusions.

5. Brain & Neurobiology — Brain Mechanisms Related to Somatic Delusions

Big picture first:

Somatic delusions = the brain is reading “signals from the body” in a distorted way + assigning wrong meaning + failing to update beliefs properly.
This is not “just overthinking.” There are real patterns of brain changes.

5.1 Three-layer model: bodily signal → salience → belief

You can think of it as three layers:

Bottom-up signal layer

Nerves from skin, muscles, and internal organs go to the spinal cord → up to the thalamus + somatosensory cortex.
They tell the brain, “This is how the body is feeling right now.”

Interpretation & salience layer

The insula + salience network keep asking,
“Is this signal important?” “Should we worry about it?”
If this system over-assigns importance to minor signals → every itch/tingle/sharp sensation becomes a big deal.

Top-down story & belief layer

The frontal–parietal network, default mode network (DMN), hippocampus, etc., help “write stories,” for example:
“This kind of itch = there must be insects under my skin.”
If the belief-updating system is impaired, then even normal test results do not shift the belief.

Neuroimaging reviews across psychotic disorders show that people with delusions (including somatic) often have gray matter changes in the dorsolateral prefrontal cortex, insula, thalamus, temporal gyrus, amygdala, etc.—precisely the networks responsible for sensing, interpreting, and believing (Frontiers).

5.2 Insula — Interoception Hub (“feeling from inside oneself”)

The insula is the brain region that “reads the inside of the body,” such as:

Racing heart

Chest tightness

Stomach pain

Itches under the skin, twitching eyelids

A sense of discomfort like poor blood circulation

Recent reviews of the insula in psychiatric disorders show that it is involved in interoception (perception of internal bodily states), emotion, arousal, and body awareness, and plays a role in psychosis, especially in delusions and hallucinations (PMC).

For somatic delusions/delusional infestation, evidence is quite strong that:

Changes in the insula + thalamus are seen most often in groups with somatic delusions compared to other delusion types (ScienceDirect +1).

MRI studies in delusional infestation show gray matter changes in the insula, prefrontal, temporal, cingulate, and striatum, interpreted as impaired prefrontal control over somatosensory information (ScienceDirect +1).

In simple terms:

The “wires” carrying information from the body are very active,

But the “internal state control center” (insula) and the “chief analyst” (prefrontal cortex) do not handle them well,

So minor signals are interpreted as major threats.

Consequences:

Minor bodily sensations = read as “serious abnormalities.”

Normal sensations = made hyper-salient (hyper-awareness).

Once these signals are fed into the belief-forming networks → they crystallize into “There is definitely something inside me.”

5.3 Thalamus + Somatosensory Cortex — Gate for sensory input + body map

Thalamus = hub through which most sensory signals pass before reaching the cortex.

Somatosensory cortex (S1/S2) = map of our body (skin, location, pressure, temperature).

Findings from research:

In people with somatic delusions/tactile hallucinations:

Somatosensory abnormalities are common in schizophrenia (impaired perception of touch, temperature, pain, etc.), and about 30–50% of first-episode psychosis cases have somatic delusions + tactile hallucinations (SpringerLink).

Some studies report hyperperfusion (excess blood flow) in the primary somatosensory cortex in people with somatic-type delusional disorder, consistent with “over-responding to bodily sensations” (Wiley Online Library).

Reviews on thalamus and psychosis show that in patients with cognitive decline + psychosis, somatic delusions such as organ rot, body being controlled from outside, invasion by parasites/disease are common and linked to the thalamus’s role in filtering/integrating bodily sensations before sending them to the cortex (Nature).

Conceptually:

If the thalamus/somatosensory cortex are “too loud, too leaky, or misprocessing,”
→ the brain receives more “strange bodily sensation” input than it should.

If this co-occurs with an abnormal insula + overactive salience network → everything is ready to be interpreted as “evidence of something wrong in the body.”

5.4 Salience Network, Dopamine & Aberrant Salience — The brain assigns “importance to the wrong things”

The salience network consists mainly of:

Anterior insula

Dorsal anterior cingulate cortex (dACC)

Its functions:

Determine which signals are “salient” and worthy of attention.

Switch focus between the Default Mode Network (inner thoughts, daydreams, self-related thinking) and the Executive Network (acting, decision-making, planning).

Classic delusion models (Kapur / Corlett) suggest:
In psychosis, there is aberrant salience = the brain gives abnormal importance to certain stimuli—sounds, lights, others’ gestures, or bodily sensations themselves (PMC +1).

Now add dopamine:

Dopamine = the module for “weighing importance + learning from the mismatch between expected and actual events (prediction error).”

If dopamine firing is mistimed/excessive/mislocalized,
→ ordinary events or minor bodily sensations feel abnormally important,
→ then the frontal cortex tries to “construct a story” to explain why they are so important,
→ that story becomes a delusion.

Corlett et al. propose that delusions arise from aberrant prediction error and impaired belief updating. The system “predict → compare with reality → revise belief” malfunctions, leaving incorrect beliefs in place (PubMed +1).

For somatic delusions:

Minor bodily signals + aberrant salience → “Whoa, this is extremely important; something must be seriously wrong inside me.”

Every little jab/itch = a distorted prediction error → reinforcing the belief that “something is inside me / my organ is failing.”

This is especially visible in cases of delusional infestation triggered by dopamine agonists (e.g., ropinirole in Parkinson’s patients), where increased dopamine has been reported to directly induce DI in some individuals (Cureus).
This shows that simply “turning the dopamine knob” can radically change the internal world.

5.5 Belief and interpretation networks (Frontal–Parietal Networks, DMN)

Delusions are not just about distorted bodily signals—they also require a “story-generating system” that holds beliefs in place.

Neuroimaging reviews show that:

Delusions are associated with gray matter reductions in:

Dorsolateral prefrontal cortex (DLPFC)
Hippocampus
Insula
Thalamus
Superior temporal gyrus, etc., across multiple disorders (schizophrenia, bipolar, Alzheimer’s, etc.) (Frontiers).

In delusional infestation, there is a consistent pattern of abnormalities in the fronto–temporo–parietal network + insula + striatum + thalamus across many studies, and some authors propose that disruptions in the sensorimotor/peripersonal network may explain somatic delusions (Dove Medical Press +2, PubMed +2).

On the cognitive side, there are biases such as:

BADE (Bias Against Disconfirmatory Evidence) = a tendency to “not accept evidence that contradicts one’s belief.”
Reviews show that people with delusional ideation often have difficulty using new information that doesn’t fit their existing beliefs. At the brain level, this is linked with changes in the DLPFC, insula, thalamus, and other networks involved in evaluating evidence and beliefs (Frontiers).

In simple picture form:

Bottom-up: bodily signals are “too loud.”

Salience & dopamine: importance is over-assigned.

Top-down: the belief system / DLPFC / DMN / hippocampus “locks in” the narrative that “My body is definitely broken.”

The belief-updating system (prediction error + executive control) is distorted → so the story doesn’t get revised.

6. Causes & Risk Factors — Causes and Risk Factors for Somatic Delusions

Very important:
There is no single cause of somatic delusions.
They usually arise from multiple layers:

Genetic and neurodevelopmental vulnerabilities

Personality/cognitive style

Life experiences and environment

Medical/neurological conditions

Substances/medications

We can divide this into layers in a “bio–psycho–social + medical + substance” framework.

6.1 Psychiatric base

Somatic delusion is a theme of delusion that can occur in several disorders (Dove Medical Press +1), such as:

Delusional Disorder, Somatic Type

Bodily delusions are the main or nearly exclusive theme.
Other domains of functioning are relatively preserved.
The person may look “normal in everything except the body issue.”

Schizophrenia Spectrum

Somatic delusions may be one of several delusion types.
They often coexist with hallucinations, disorganized speech, and negative symptoms.
Somatosensory deficits and tactile hallucinations are common in schizophrenia and can link to somatic delusions (SpringerLink).

Mood Disorders with Psychotic Features

e.g., Major depressive episode with psychotic features.
Somatic themes may be tied to guilt/hopelessness, such as “My organs are rotten, I’m poisonous to others,”
Or take a Cotard-like form, e.g., “I’m dead, my organs are rotting inside.”

OCD / BDD / Somatic-type OCD

In DSM-5, OCD and BDD have insight specifiers (good/fair vs poor vs absent/delusional beliefs) (American Psychiatric Association +2; practicum support-psych.sites.olt.ubc.ca +2).
In BDD or OCD with absent/delusional insight, beliefs about appearance or contamination can reach delusional intensity.
Clinically, this can overlap with somatic delusion.

In summary:
If a person already has a psychiatric base (schizophrenia spectrum, mood disorder with psychotic features, OCD/BDD) → the probability that psychotic symptoms will “choose a somatic theme” is higher.

6.2 Medical & Neurological Conditions

This layer is critical for “not missing things,” because many cases involve:

Real bodily symptoms (itch, pain, odd sensations) from medical/neurological conditions,

Which are then over-interpreted by the mind into somatic delusions,

Or psychosis secondary to a medical condition, with somatic content.

Examples (not exhaustive, but showing patterns):

Neurodegenerative diseases / certain dementias

Reviews on thalamus and psychosis note that in dementia patients who develop psychosis, somatic delusions such as body control by external forces, infestation, organ rot, etc., are common (Nature).

Conditions with sensory neuropathy/peripheral nerve involvement

These can cause strange sensations like burning, itching, stinging, or sharp pains.
In someone psychologically/cognitively vulnerable, this increases risk of delusional interpretations.

Endocrine/metabolic/autoimmune deficiencies

e.g., thyroid disorders, vitamin B12 deficiency, etc.,
Can affect the brain and lead to secondary psychosis.

Real skin diseases + high distress

Mild or chronic dermatologic conditions → increased somatosensory triggers.
In some individuals, stress + preoccupation shifts belief from “I have sensitive skin” to “There is something living under my skin for sure.”

In real clinical practice, when somatic delusion appears, one must thoroughly screen for physical and neurological diseases first, and only then conclude that the remainder is delusional/psychotic disorder.

6.3 Substances & Medications

Certain substances can:

Overactivate dopamine systems,
Induce tactile hallucinations,
Or disturb the brain sufficiently to cause secondary psychosis with somatic themes.

Examples:

Stimulants

e.g., amphetamines, cocaine (brand names omitted).
Commonly produce paranoid delusions + tactile hallucinations (“something is crawling on me”).
With chronic/high-dose use, somatic delusions in infestation form are frequent.

Dopamine agonists / Parkinson’s medications

Case reports and reviews show that dopamine agonists such as ropinirole can trigger delusional infestation in individuals with underlying brain vulnerability (Cureus).
This reinforces the link dopamine → salience → somatic delusion.

Steroids / certain medications

High-dose steroids or drugs with psychiatric side effects can cause transient psychosis.
Themes may be persecutory, grandiose, or somatic, depending on the patient’s background.

Withdrawal

Abrupt withdrawal from certain substances/medications (e.g., benzodiazepines, severe alcohol withdrawal) can induce hallucinations and delusions, including somatic delusions.

6.4 Psychological & Cognitive Factors

This layer describes “how the brain interprets experience,” and is crucial in explaining why people exposed to similar bodily signals end up with very different beliefs.

Examples of cognitive traits/patterns:

Somatosensory Amplification

Concept: no major physical pathology, but the person “feels every bodily sensation more intensely than others.”
It’s like the volume of bodily signals is turned up.
Combined with catastrophic thinking (“everything is dangerous”), this can push things toward somatic delusions.

Jumping to Conclusions (JTC)

Trait: making rapid decisions with little data.
In people with delusions, this bias is common—feeling or noticing something small → quickly concluding “It must be X.”
For example, 3 days of itch → “Something has entered my body already,” and the rest of their behavior is just searching for “evidence” for that conclusion.

Bias Against Disconfirmatory Evidence (BADE)

An unwillingness to accept evidence against one’s belief.
If the belief = “I’m rotting / I have something under my skin,” then normal blood/scan/skin exam results are interpreted as “The doctor isn’t competent,” rather than “Maybe it’s not what I thought” (Frontiers).

High trait anxiety / neuroticism / health anxiety

People who are temperamentally prone to anxiety, easily suspicious about health, and amplify risk in their head → small bodily signals become fuel for intense body-centered narratives.
When combined with biological risk for psychosis, the chance of developing somatic delusions increases.

6.5 Life Events & Sociocultural Factors

Unexplained bodily experiences

For example, a history of strange physical symptoms that doctors failed to diagnose, or being told “it’s all in your head.”
The brain may learn, “No one can explain my body; I must interpret it myself.”
When psychosis emerges, the self-generated story can crystallize into a delusion.

Trauma / abuse / neglect

Many psychosis studies show that childhood/adolescent trauma (especially body-related violation or abuse) is linked to delusions themed around the body and threat.
For somatic delusions, although the evidence is not as dense as for persecutory delusions, the direction is similar: the body is the “field of past harm,” so later the brain may treat body signals as dangerous and misinterpret them.

Social isolation, shame, stigma

Those who already feel ashamed of their body/odor/appearance → if psychosis starts, a somatic theme can easily build upon these old beliefs.
Once they believe “I smell bad / I’m deformed / I’m gravely ill,” they withdraw socially → real-world input decreases → beliefs are less challenged → they harden further.

Culture & health beliefs

Some cultures emphasize bodily purity or cleanliness/odor/“contamination” as morally important.
If someone grows up in such a framework, then when psychosis appears, the somatic theme will be “wrapped” in that cultural schema.

6.6 Other individual factors

Age of onset

If somatic delusions begin in youth along with other psychotic symptoms → schizophrenia spectrum/delusional disorder is considered first.
If they begin later in life, with cognitive decline or cerebrovascular disease, etc. → dementia/medical/medication causes become more likely (Nature +1).

Genetics/family history

Family history of psychotic disorders, mood disorders, OCD/BDD, etc., increases biological vulnerability.
But which delusional theme emerges (persecutory, somatic, grandiose, etc.) still depends on life experiences and cultural context.

Premorbid personality

Personality with strong bodily focus, perfectionism about appearance, longstanding health anxiety patterns → more likely to form somatic themes.
Paranoid traits → when psychosis emerges, bodily symptoms may be interpreted as “someone poisoned me” rather than as spontaneous illness.

6.7 Integrated overview across layers

Let’s combine everything into one “storyline”:

A person has a vulnerable biological base (genetics + slight abnormalities in dopamine/insula–thalamus–somatosensory networks).

They also have certain personality/cognitive styles, such as:

Somatosensory amplification (over-feeling bodily signals)
High health anxiety
Jumping to conclusions and BADE (not accepting contradicting evidence).

They accumulate life experiences, such as:

Having had strange illnesses where no doctor could explain the symptoms
Being mocked or shamed for their smell/appearance.

At some point, the brain enters psychosis mode (triggered by stress, medical disease, medication, substance, or the natural progression of a psychiatric disorder).

The salience + dopamine system becomes aberrant.
Bodily signals are amplified → itch/tingle/sharp/tight sensations feel unusual.

The frontal–parietal network + DMN try to “write a story” to make sense of these signals.

The story fits their pre-existing body-related fears.
→ It solidifies into the belief: “There is something inside me / my organs are rotten / I smell horribly.”

Every bodily sensation now becomes “confirmatory evidence.”

Safety behaviors (scratching, picking, doctor visits, checking) produce new injuries and sensations.
This spins the belief tighter and more convincing.

The prediction error/learning system malfunctions → contradictory evidence is not used.

Normal test results are interpreted as “The doctor isn’t telling me the truth,” rather than diminishing the belief.

This explains why somatic delusions are so treatment-resistant, and why we need:

Thorough screening for medical/substance causes.

Medication (especially antipsychotics, and in some cases SSRIs if OCD/BDD is comorbid).

Psychotherapy that targets beliefs, salience, and behaviors (e.g., CBTp, reduction of safety behaviors, building alternative narratives that do not reinforce the delusion).

7. Treatment & Management — Treatment and Management

This section is an educational overview, not personalized medical advice (actual treatment always depends on context/comorbidities/medical status/medications).

A) Core principle: “Evaluate thoroughly first, then plan collaboratively.”

Assess psychotic symptoms (hallucinations, command auditory hallucinations, etc.), mood, and risk to self/others.

Conduct appropriate investigations to rule out medical/neurological/substance causes.

Systematically differentiate from SSD/IAD/BDD/OCD (SciELO +1).

B) Medications (common approaches depending on etiology)

Antipsychotics are the mainstay when delusions are part of psychotic disorders.

When BDD/OCD or strong obsessive–compulsive loops are prominent: SSRIs + targeted CBT are often considered.

In delusional infestation, collaboration with dermatology/medicine may be needed to manage wounds/picking while avoiding “treatments” that reinforce the delusion.

Clinical review articles discuss the diagnosis and treatment of somatic delusions, including delusional parasitosis/Morgellons, and emphasize their placement under delusional disorder, somatic type in DSM-5-TR (Psychiatrist.com).

C) Psychotherapy and communication skills (very important)

CBT for psychosis (CBTp):

Works with interpretation of evidence, reduction of safety behaviors, and management of distress.

Motivational approaches + strong therapeutic alliance:

Avoid direct confrontational “head-on arguing” with the delusion, as it often makes it more rigid.
Use a frame like: “Validate the suffering” + “Create space to review hypotheses,” e.g.,
“I believe you really are suffering. Let’s first reduce the itch/pain, and at the same time explore several possible explanations together.”

D) Multidisciplinary care

Psychiatry + internal medicine/dermatology/neurology (depending on themes).

Plan to reduce unnecessary repeated tests while still ensuring medical safety.

8. Notes — Key “Don’t-Miss” Points

Somatic delusion ≠ somatic symptom disorder:

One is “false belief at delusional level,”
The other is “bodily symptoms + distress/preoccupation” without necessarily having delusional beliefs (SciELO).

BDD with absent insight can look very delusional, and DSM-5 highlights insight specifiers for accuracy in treatment planning (American Psychiatric Association).

If tactile hallucinations (itch, crawling, burrowing) are present, consider both delusional infestation and medical/substance factors (Psychiatrist.com).

High-risk cases (self-harm to “remove foreign bodies,” ingestion of dangerous substances to self-treat, attempts at self-surgery, etc.) must be treated as psychiatric emergencies.

Read Schizophrenia

🔎 References on Somatic Delusions / Somatic-Type Delusional Disorder

Basic definitions & diagnostic criteria

APA Dictionary of Psychology – Somatic delusion: definition as false beliefs about bodily function or organs, e.g., belief that organs are diseased or damaged (APA Dictionary).
APA Dictionary of Psychology – Delusional disorder: outlines subtypes including somatic type (body/health/appearance content) (APA Dictionary).
DSM-IV → DSM-5 / DSM-5-TR changes (NCBI + APA PDF): tables comparing Delusional Disorder criteria (removal of “nonbizarre,” emphasis on somatic subtype) (ncbi.nlm.nih.gov +1).
Cleveland Clinic – Delusional Disorder: Causes, Symptoms, Types & Treatment: overview of Delusional Disorder and subtypes, including somatic, emphasizing “fixed, unshakable beliefs” about illness/body (Cleveland Clinic).
Verywell Mind – Delusional Disorder: Symptoms, Causes, and Treatment (Verywell Mind).

Somatic delusions / delusional infestation / Morgellons

“Somatic Delusions: An Approach to Diagnosis and Treatment” – The Primary Care Companion for CNS Disorders: review of somatic delusions, delusional infestation, olfactory reference syndrome, Morgellons, differential diagnosis, and treatment; notes DSM-5-TR places ORS under OCD when insight is delusional (Psychiatrist.com).
Hylwa et al., 2018 – Delusional infestation versus Morgellons disease: argues Morgellons is a form of delusional infestation, not a separate somatic disease; emphasizes delusional belief about infestation/fibers as psychotic core (ScienceDirect +2; JAAD +2).
Freudenmann & Lepping, 2009 – Delusional Infestation | Clinical Microbiology Reviews: classic review of delusional infestation (delusional parasitosis), covering diagnostic criteria, differential diagnosis, antipsychotic treatment (ASM Journals).
Mayo Clinic – Delusional parasitosis: popular-level explanation describing Morgellons-like phenomena within delusional infestation and emphasizing psychotic etiology (Mayo Clinic).

Brain & Neurobiology

Dudina et al., 2025 – Structural and functional alterations in different types of delusions: review showing somatic delusions & delusional infestation often involve insula and thalamus changes compared with other delusion types (ScienceDirect).
Spalletta et al., 2013 – Fronto-thalamic volumetry markers of somatic delusions: somatic delusion patients show reduced left fronto-insular gray matter and thalamic involvement (ScienceDirect).
Huang et al., 2017 – Decreased Left Putamen and Thalamus Volume Correlates with Delusions: gray matter reductions in left putamen and thalamus in delusional vs non-delusional patients and controls, supporting thalamic role in psychosis (Frontiers).
Chan et al., 2020 – Structural and functional alterations in Morgellons/delusional infestation: structural/functional changes in itch/somatosensory processing regions, including insula, thalamus, sensorimotor cortex (PubMed).
Laketić et al., 2025 – Insular Cortex: Biology and Its Role in Psychiatric Disorders: review of insula’s roles in interoception, salience, emotion, body awareness, and psychosis, including somatic-type symptoms (PMC).
Onofrj et al., 2023 – The central role of the Thalamus in psychosis: links psychosis (including somatic delusions) with thalamic roles in sensory gating, noting that dementia/PD-DLB psychosis often features somatic themes (Nature +1).
Corlett et al., 2010 – Toward a neurobiology of delusions: proposes delusions as arising from abnormally computed prediction error + aberrant salience (dopamine) and how this maps onto belief formation (behavioralhealth2000.com).

Differential diagnoses: Somatic Symptom / BDD / OCD

DSM-5 Somatic Symptom and Related Disorders – workingfit summary: outlines Somatic Symptom Disorder criteria (distress + thoughts/behaviors about symptoms rather than delusional belief) as a conceptual contrast (workingfit.co.uk).
Aravind et al., 2006 – Body dysmorphic disorder, dysmorphophobia or delusional disorder?: addresses BDD, dysmorphophobia, and overlap with delusional disorder, especially in absent-insight/delusional cases (PMC).
Highlights of Changes DSM-IV-TR to DSM-5 – APA: clarifies moving OCD/BDD with absent insight (delusional beliefs) out of Delusional Disorder and adding insight specifiers to OCD-related disorders (American Psychiatric Association).

Somatic delusion / Somatic-type delusional disorder / Delusional disorder somatic type / Delusional infestation / Delusional parasitosis / Morgellons disease / Ekbom syndrome / Olfactory reference syndrome / Psychosis and body symptoms / Body-focused delusions / Tactile hallucinations / Itch and psychosis / Insula and somatic delusions / Thalamus and psychosis / Salience network / Aberrant salience / Prediction error and delusions / Health anxiety vs somatic delusion / Somatic symptom disorder vs delusional disorder / Body dysmorphic disorder with absent insight / OCD with poor insight / Secondary psychosis due to medical condition / Substance-induced psychotic disorder / Differential diagnosis of somatic delusions / Treatment of somatic delusions / Antipsychotic treatment / CBT for psychosis / Neurobiology of delusions / Psychotic disorders DSM-5-TR

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