Visual hallucinations

1. Overview — What are Visual Hallucinations?

Visual hallucinations are experiences in which a person sees something with their own eyes even though, in objective reality, nothing is actually there in that space. This can include people, animals, shadows, shapes, lights and colors, objects, or even entire scenes and events.

The key point is that the brain is “creating” these images by itself, but the person feels:

“I really saw it with my own eyes — at that moment it felt completely real.”

So this is not just:

• Imagining a picture in one’s mind (mental imagery)

• Daydreaming

• Or deliberate fantasy where the person knows they are “just thinking it up”

For someone who is experiencing visual hallucinations, the experience in front of them is perceived as “real” at a sensory level — as a full sensory (visual) event — at least during the period when the symptom is occurring.

Clinically, visual hallucinations are not a disease by themselves. They are a symptom that can appear in many different conditions, such as:

• Schizophrenia spectrum and other psychotic disorders

• Delirium (acute confusional state), especially in older adults or critically ill hospitalized patients

• Certain types of dementia, such as Dementia with Lewy bodies and Parkinson’s disease dementia

• Conditions related to eye disease and vision problems, such as Charles Bonnet syndrome in people with very poor eyesight or significant visual loss

• States caused by medications, drugs, or alcohol — both during intoxication and during withdrawal

What makes visual hallucinations clinically important is that they can:

• Indicate underlying brain abnormalities or specific neurological conditions

• Be associated with medical emergencies, such as delirium from severe infection or serious metabolic problems

• Directly affect everyday safety, for example:
• Seeing something “rush toward them” and quickly dodging, causing them to fall
• Suddenly braking while driving because they see something that is not there
• Running away from something that does not exist in reality

How are visual hallucinations different from “mis-seeing / misinterpreting” (illusions)?

• An illusion means there is a real object or stimulus, but the brain misinterprets it — for example, seeing clothes hanging in a dark room and feeling as if “someone is standing there.”

• A visual hallucination means there is nothing there at all, but the brain creates an image that the person “sees” as if it were really present.

In many cases, visual hallucinations occur together with other symptoms, such as:

• Auditory hallucinations (hearing voices or sounds that are not there)

• Delusions, such as believing that someone is following them or watching them

• Disorganized thinking or behavior that is very different from their usual behavior

However, in some conditions (for example, Charles Bonnet syndrome or certain phases of Lewy body dementia), visual hallucinations may be the prominent feature, without clearly noticeable auditory hallucinations like those commonly seen in schizophrenia.

Key points to remember when understanding visual hallucinations:

• There must be no real external stimulus in front of the person.
  It is not just “seeing wrong” or “misinterpreting” something; there is no object that can explain the image seen.

• The person often believes that what they see is “real”, at least at that moment.
  Some people may later wonder whether it was a hallucination, but at the time it happened, it felt very real.

• Visual hallucinations are a cross-diagnostic symptom:
• They can be found in schizophrenia spectrum disorders
• They are common in delirium, dementia, Parkinson’s disease, and Lewy body dementia
• They can be caused by drugs/medications, intoxication, or withdrawal
• They can also arise from eye diseases or focal brain conditions, such as occipital lobe lesions, brain tumors, stroke, or Charles Bonnet syndrome

• Cultural and religious context also influences interpretation.
  

  In some cultures, “seeing a holy being / deity / spirit” may be interpreted within a religious or cultural framework and is not automatically considered a psychiatric symptom.
  
  The role of clinicians and therapists is to carefully distinguish what counts as a true mental/brain symptom versus what lies within the normal range of that culture’s context.

In simple terms:

Visual hallucinations = the brain “going big” and generating images on its own.
And the person feels as if they are truly seeing something with their eyes, even though, in reality, there is nothing there at all.

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2. Core Symptoms — Main Clinical Features of Visual Hallucinations

From a clinical perspective, when doctors take a history about visual hallucinations, they do not just ask:

“Do you see anything?”

and then stop. Instead, they try to break the big picture down into several dimensions, for example:

• What exactly do you see?

• How clear is it?

• When does it happen?

• Do you realize it might not be real?

• How is it affecting your life?

This helps them judge which type of condition the hallucinations point toward and how dangerous the situation might be.

2.1 Characteristics of What is Seen (Phenomenology of the Image)

This part is very important, because the “appearance” of the hallucination can give hints about the underlying brain mechanisms.

2.1.1 Simple Visual Hallucinations (Elementary)

These are simple images, not complex in form. For example:

• Flashes of light, bright flickers, streaks of light passing across vision

• Dots (spots), small lights like fireflies

• Geometric patterns, such as zigzags, circles, overlapping shapes

• Patterns on walls or floors that seem to “move” or twist by themselves

• Colored bands or a scintillating scotoma like in migraine

Important properties:

• They often show repeated patterns (for example, the same zigzag pattern each time).

• They usually are not “clearly formed people/animals/objects”, but more like light, shapes, or patterns.

• Their emotional meaning is generally less intense than complex hallucinations:

– The patient may feel strange, confused, or annoyed, rather than feeling as if someone is about to kill them.

Neuro-wise:

• They often involve lower levels of the visual system, such as the retina, optic nerve, lateral geniculate nucleus, and primary visual cortex (V1).

They are found in:

• Migraine aura, especially visual aura

• Occipital lobe epilepsy (flashing lights before a seizure)

• Brain lesions involving the occipital / visual cortex

• Certain toxic/metabolic states that cause cortical hyperexcitability

2.1.2 Complex Visual Hallucinations

These are hallucinations that are realistic and more complex than simple ones, for example:

• Seeing full people (who may be familiar or strangers)

• Seeing animals (cats, dogs, snakes, rats, insects crawling all over the wall)

• Seeing strange characters or unusual beings

• Seeing entire scenes, such as a crowd of people walking by, a room filled with people, or landscapes

• Seeing moving scenes with a storyline, such as a person walking in, sitting down, looking at you, etc.

Properties:

• They have high detail (faces, clothes, facial expressions, movement).

• They often carry strong emotional meaning:
• Some people feel warmth (e.g., seeing a loved one who has died)
• Some feel intense fear (e.g., seeing people staring at them threateningly, seeing frightening animals, etc.)

• Sometimes the hallucinated figures interact with the patient, such as:
• Looking back at them
• Reaching out towards them
• Appearing as if about to attack

In terms of causes, complex visual hallucinations are found in many conditions, such as:

• Psychotic disorders (schizophrenia, schizoaffective disorder, etc.)

• Delirium (e.g., older adults with infections, pneumonia, sepsis, etc.)

• Dementia with Lewy bodies (visual hallucinations are a core feature)

• Parkinson’s disease psychosis

• Charles Bonnet syndrome in people with severe vision loss (images are often clear, colorful, and highly detailed)

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2.2 Insight — How Strongly Does the Person Believe It Is “Real”?

A key question is:

“At that time, how real did it feel to you?”

The level of insight helps distinguish whether the symptom leans toward strong psychosis or is more of a brain/eye phenomenon in another context.

2.2.1 100% Belief That It Is Real (No Insight)

The patient is completely convinced that:

“There really is a person standing there.”
“There really are animals all over the room.”

They may argue strongly with doctors or family if someone says, “There’s nothing there.”

Often seen in:

• Psychotic disorders (schizophrenia spectrum), especially when delusions are also present

• Delirium in very confused states (patients may be aggressively frightened)

2.2.2 Some Doubt (Partial Insight)

The patient says things like:

“At that time it felt very real, but when I look back, I don’t think it was really there…”
or
“I did see it, but it also felt strange, like it probably wasn’t actually real.”

Seen in:

• Migraine aura

• Sleep-related hallucinations (hypnagogic/hypnopompic)

• Some cases of Charles Bonnet syndrome, where insight improves once the mechanism is explained

2.2.3 Clear Awareness That “It’s a Hallucination” (Good Insight)

Some people say directly:

“I know it’s a hallucination, but I still keep seeing it — it’s annoying or scary.”

Seen in:

• Patients who have repeated experiences and have received clear diagnosis and explanation

• Charles Bonnet cases who know it is due to vision problems

• People who have hallucinations but maintain good baseline insight

This level of insight is very important for treatment planning, such as using CBT for psychosis and teaching specific coping strategies.

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2.3 Context — When and Under What Circumstances Do They Occur?

The combination of “what the hallucination looks like” + “when it appears” is a very useful clue to the underlying cause.

2.3.1 When Very Sleepy / Sleep-Deprived / During Sleep–Wake Transitions

• Hypnagogic hallucinations: occur when falling asleep

• Hypnopompic hallucinations: occur when waking up

Characteristics:

• Often a hazy, half-dream, half-awake state

• Hallucinations may appear as brief flashes, e.g., seeing someone standing next to the bed or seeing a shadow lying on top of them

• Many people have these occasionally during times of stress and sleep deprivation → this does not necessarily mean they have a disorder

However, if they occur very frequently and are accompanied by other symptoms such as sleep paralysis or daytime sleepiness, one might think of narcolepsy or other sleep disorders.

2.3.2 During Severe Illness / High Fever / Hospitalization

If a patient is:

• Older, or

• Has chronic medical conditions, and suddenly:
• Becomes confused and disoriented (not knowing the date, place, or situation)
• Loses focus easily during questioning
• Sees people or animals in the room when no one is there

→ This points toward delirium (acute confusional state).
This is a medical emergency, often caused by infections, organ failure, drug toxicity, etc.

2.3.3 During Drug Intoxication / Withdrawal / Use of Hallucinogenic Substances

Visual hallucinations can occur during:

• Intoxication (while high) from LSD, psilocybin, methamphetamine, MDMA, etc.

• Withdrawal, such as:
• Alcohol withdrawal (delirium tremens)
• Benzodiazepine withdrawal

Characteristics:

• Images may have intense or distorted colors, strange patterns, warped shapes

• Fear and paranoia can be very high

• There may also be tactile hallucinations (e.g., feeling insects crawling on the skin)

2.3.4 In People with Poor Vision / Partial Blindness

Patients with:

• Macular degeneration

• Glaucoma

• Retinitis pigmentosa

• Diabetic retinopathy

• Very severe cataracts

• Etc.

Their brains receive much less input, which can lead to Charles Bonnet syndrome.

Characteristics:

• Images are very clear, colorful, and detailed (complex hallucinations)

• The content often does not relate directly to their life (e.g., seeing historical figures, seeing strange buildings)

• The underlying eye condition does not directly cause psychotic thinking → many patients have good insight, but feel frightened or confused

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2.4 Impact on Life (Impact & Functional Impairment)

Hallucinations are not just “weird experiences” — they can genuinely disrupt and damage a person’s life.

2.4.1 Emotional Impact

Fear and anxiety can be very high, especially when:

• The hallucinations have threatening content (e.g., figures that seem to want to harm them)

• There are delusions alongside the hallucinations (e.g., believing the figures intend to attack)

Some people feel ashamed and do not dare tell anyone → they end up suffering in silence.

If the hallucination involves loved ones who have died, the experience can cause mixed feelings — both comforting and very sad at the same time.

2.4.2 Behavior and Safety

The patient may:

• Run away or dodge what they see → risking falls and accidents

• While driving, see something that isn’t real and slam on the brakes → extremely dangerous

• Use knives/weapons to “protect themselves” from what they see

In older adults with dementia/delirium, this can lead to:

• Wandering
• Getting lost
• Falls
• Refusal of treatment

2.4.3 Work and Relationships

• Concentration worsens because they are constantly battling or monitoring what they see.

• Jobs that require high precision or safety (e.g., driving, operating machinery) may become almost impossible.

• Family and others may not understand, thinking the person is “overreacting” or “being ridiculous,” which can lead to conflict and reduced social support.

2.4.4 Sleep and Overall Quality of Life

• If hallucinations frequently occur at night, the person may begin to fear the dark and fear sleeping alone.

• Sleep patterns deteriorate → insomnia or difficulty falling asleep → which in turn worsens hallucinations because sleep deprivation itself increases the risk of hallucinations.

In summary, the core symptoms of visual hallucinations are not just “seeing things that are not there.” They include:

• The nature of the images (simple vs complex)

• The person’s insight into what they see

• The context and timing in which they occur

• The impact on emotions, behavior, safety, and daily functioning

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3. Diagnostic Criteria — Diagnosis (Linking to DSM-5-TR / ICD-11)

This is very important: in DSM-5-TR and ICD-11,

“Visual hallucinations” = a symptom,
not a standalone diagnosis like Schizophrenia or Delirium.

When clinicians diagnose, they work in two stages:

• First — check whether what the patient describes truly qualifies as a hallucination.

• Then — once it is clear that it is a hallucination, they ask:

“In which disorder is this hallucination occurring?”

3.1 Basic Criteria for Calling Something a “Hallucination”

There are several key components (which apply to visual, auditory, etc., but here we focus on visual):

Perception-like experience

• An experience similar to genuine sensory perception.

• For visual hallucinations: the patient feels they see something with their eyes as if it were normal vision (with color, shape, distance, etc.).

No external stimulus (no real object)

• In reality, there is nothing there.

• If we examine the environment and find no object that could explain the image, this criterion is met.

Experienced as “coming from outside”

• The patient feels that “it is outside my body,” not merely a picture in their mind.

• For visual hallucinations: it feels as if the image appears in physical space (on the wall, in the room).

Contradicts reality and is not a normal religious or cultural experience

• If it is a “vision” or a religious experience that is considered normal in that community/religion and does not impair functioning, it is usually not counted as a clinical hallucination.

• The key point is whether it impairs daily functioning or clearly conflicts with the shared reality (consensus) of most people.

If all four criteria are met, we can confidently call it a “hallucination.”
After that, we look more specifically at whether it is visual, auditory, tactile, etc.

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3.2 Differentiating from Illusion / Pseudohallucination / Imagination

These three are similar enough to cause confusion. If we fail to separate them, we may over-diagnose hallucinations.

3.2.1 Illusion (Misperception of a Real Object)

An illusion is a misperception of a real stimulus. For example:

• In a dark room, seeing clothes draped over a chair and feeling as if “someone is standing there”

• Seeing moving tree shadows and feeling as if someone is walking behind you

Key points:

• There is a real object (real stimulus) present.

• The brain misinterprets it due to low light, fear, expectations, etc.

Clinically:

• Illusions are experiences that many healthy people can have.

• But if they occur very frequently and cause significant distress along with other symptoms, they may reflect underlying anxiety, trauma, etc.

However, they are not hallucinations in the strict sense.

3.2.2 Imagination / Imagery

This is “creating images on purpose” in the mind, with full awareness that they are internal and not real.

People might say:

“Imagine if a ghost appeared there — what would it look like?”

→ This clearly is not a hallucination.

Key points:

• There is some degree of control (you can more or less decide to imagine or stop imagining).

• There is meta-awareness: the person knows, “I am imagining this.”

3.2.3 Pseudohallucination

This term is used inconsistently across the field, but the common concept is:

• The patient has an experience similar to a hallucination,
  but feels (at least partially) that “this probably isn’t real,” or feels that “it is inside my head rather than outside.”

It is often used in contexts such as:

• PTSD

• Dissociative phenomena

• States while using certain drugs/substances

Distinguishing points:

• A full-blown hallucination → the patient typically experiences it as “out there” (outside the body), as if truly seen through the eyes.

• A pseudohallucination → feels more like an “intrusive inner image”; even though the person can’t control it, they can somewhat distinguish that it is not real.

For a Nerdyssey article, you can add a short comparison table, for example:

• Is there a real stimulus?

• Does the person know they are imagining?

• Is the experience “inside the head” or “out in the world”?

• How strong is the belief that it is real?

This helps readers separate the concepts clearly.

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3.3 In Which Diagnoses Do Visual Hallucinations Appear?

As mentioned: visual hallucinations are a symptom.
To arrive at a diagnosis, we must consider the whole cluster of symptoms + duration + cause.

Examples of major diagnostic groups where visual hallucinations play an important role:

3.3.1 Schizophrenia / Schizoaffective / Schizophreniform

Even though auditory hallucinations are more classic, visual hallucinations do occur, especially in cases where:

• The illness is severe

• There are comorbid neurological issues

Here, hallucinations (including visual) count under the “Hallucinations” component, which is part of Criterion A for schizophrenia spectrum disorders.

The symptom cluster usually includes:

• Delusions

• Disorganized speech

• Disorganized or catatonic behavior

• Negative symptoms (e.g., avolition, flat affect, etc.)

3.3.2 Delirium

Visual hallucinations + acute onset + fluctuating consciousness + inattention
→ This combination is highly suggestive of delirium.

Key points:

• The change appears over hours to days (not on-and-off over months).

It is commonly seen in:

• Older adults
• Patients admitted to the hospital
• People with infections, organ failure, drug toxicity, etc.

If visual hallucinations are seen in an older person who has just arrived in the ER, we must think of delirium first, before assuming a primary psychotic disorder.

3.3.3 Major / Mild Neurocognitive Disorder (Dementia)

Especially:

• Dementia with Lewy bodies (DLB)
  – Vivid, recurrent visual hallucinations are a core clinical feature.
  – The content is highly detailed and clear, almost like watching a movie.

• Parkinson’s disease dementia / Parkinson’s disease psychosis
  – Visual hallucinations are common in long-standing Parkinson’s disease, especially with dopaminergic medication.
  – Initially, some patients may have good insight, but this can worsen over time.

In Alzheimer’s disease, visual hallucinations are not as prominent as in DLB, but in middle-to-late stages, psychosis (including visual hallucinations) can occur, especially when there are psychotic features.

3.3.4 Substance/Medication-Induced Psychotic Disorder

DSM-5-TR includes specific diagnoses for cases where hallucinations/delusions arise in the context of:

• Substance use (amphetamines, cocaine, LSD, cannabis, etc.)

• Substance withdrawal (alcohol, benzodiazepines, etc.)

• Use of certain medications at high doses (steroids, anticholinergics, etc.)

We must distinguish this from:

• Primary psychotic disorders where the person happens to be using substances.

We look at the timeline: did symptoms begin in relation to starting/increasing or stopping a substance?

3.3.5 Psychotic Disorder Due to Another Medical Condition

This diagnosis is used when there is clear evidence that hallucinations (including visual) are due directly to another medical condition, such as:

• Brain tumor

• Epilepsy (especially occipital lobe epilepsy)

• Autoimmune encephalitis

• Metabolic encephalopathy

• Wilson’s disease

• Neuroinfections, etc.

In such cases, doctors use this diagnosis instead of schizophrenia, because the cause is clearly organic (medical/neurological).

In this group, visual hallucinations often occur along with:

• Other neurological symptoms (seizures, focal deficits, severe headache, etc.)

• Changes in consciousness (altered consciousness) or cognitive decline

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4. Subtypes or Specifiers — Types / Forms of Visual Hallucinations

There are no official specifiers in DSM-5-TR specifically for visual hallucination subtypes, but clinically, we often divide them into categories to help think about causes:

4.1 Classified by “Complexity of the Image”

Simple (elementary) visual hallucinations

• Flashes of light, colored spots or bands, zigzag lines, geometric patterns

• Often associated with the occipital lobe, visual pathway, epilepsy, and migraine aura

Complex visual hallucinations

• Seeing people, animals, insects, objects, characters, realistic scenes, moving images

• Common in psychosis, delirium, dementias, Charles Bonnet syndrome, Parkinson’s psychosis

4.2 Classified by “Theme / Content”

• Scary / Threatening → seeing shadowy figures, dangerous animals, ghosts, demons
  → Common in persecutory psychosis, delirium, and severe depression with psychotic features

• Neutral / Non-threatening → seeing a stranger standing somewhere, seeing a cat sitting on a chair, etc.
  → Seen in dementia, Charles Bonnet syndrome, hypnagogic hallucinations

• Bizarre / Impossible → seeing things that violate physical laws, such as warped buildings, cartoon characters stepping out into real space, etc.
  → May count as bizarre content when writing up a case report

4.3 Classified by “Time Pattern”

• Hypnagogic hallucinations — when falling asleep

• Hypnopompic hallucinations — when waking up

• Continuous / daytime hallucinations — occurring frequently throughout the day → think of psychosis, dementia, delirium, substance-related conditions

4.4 Classified by “Level of Insight”

• With poor/no insight → firmly believed to be real

• With partial insight → sometimes believed, sometimes doubted

• With good insight → recognized as symptom/hallucination

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5. Brain & Neurobiology — Underlying Brain Mechanisms

When we talk about visual hallucinations, what we are really talking about is:

“The brain is generating images on its own, even though there is no external sensory signal at that location.”

It is not just the mind “thinking too much.” It is a phenomenon involving neural networks that are out of sync or out of balance between bottom-up signals from the eyes and top-down predictions from the brain.

5.1 Visual System & Cortical Networks — Visual Pathways and Cortex

Normally, “seeing” follows a pipeline like this:

retina → optic nerve → optic chiasm → optic tract → lateral geniculate nucleus (LGN) in the thalamus → primary visual cortex (V1) → higher visual areas (V2, V3, V4, MT, etc.) → association cortex that connects to memory, emotion, and attention

Clinically speaking, we can divide it into:

• Lower levels (early visual system)
  – retina, LGN, V1
  – handle basic features such as light, lines, movement, and basic color

• Higher levels (higher-order visual & association areas)
  – ventral stream (“what” pathway: shapes, objects, faces, letters)
  – dorsal stream (“where/how” pathway: location, motion, spatial relationships)
  – plus hippocampus, amygdala, prefrontal cortex for memory, emotion, and belief

When this system malfunctions, different types of hallucinations emerge:

Simple hallucinations ↔ lower-level system misfiring

If there is hyperexcitability or disinhibition in areas such as:

• The retina (for example, in some cases of retinal detachment with flashing lights)

• The LGN

• The primary visual cortex (V1)

We often get:

• Flashes of light

• Geometric patterns

• Light spots

• Twisting or moving patterns on surfaces

This aligns with simple visual hallucinations that involve only basic shapes, colors, or motion.

Complex hallucinations ↔ higher-level systems + memory/emotion networks

If the abnormality involves:

• Temporal–occipital regions (areas that process faces and objects)

• Parietal–temporal–occipital junction

• Limbic system (amygdala, hippocampus)

• Prefrontal cortex

Then the brain begins to “assemble images” into familiar forms, such as:

• Full people

• Animals

• Rooms or indoor scenes

• Buildings

And it adds emotion and meaning on top of them → resulting in complex visual hallucinations that can be beautiful, terrifying, and very realistic.

In conditions like Dementia with Lewy bodies and Parkinson’s psychosis, much evidence points to abnormalities in:

• Visual association cortex

• Cholinergic systems

• Networks linking attentional and executive control

This leads to hallucinations that are:

• Highly detailed

• Very vivid

• Recurring with similar patterns

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5.2 Top-Down Prediction & Predictive Coding — Overpowering Predictions / Weak Input

Modern theories move away from the idea that hallucinations are just “broken brains,” and instead frame them in terms of predictive coding:

The brain is a machine that constantly “predicts the world.”
It compares top-down predictions with bottom-up sensory input.
If they match → we experience normal perception.
If they do not match → the brain updates its internal model or distorts perception.

In visual hallucinations, there are two major patterns:

Top-down predictions are too strong

• Dopamine/serotonin or certain networks become overactive.

• The brain strongly “pushes” its own predictions into perception, insisting that something should be seen.

• The sensory input (bottom-up error signals) are suppressed or ignored.
  → The result is hallucinations with specific meanings, such as seeing people believed to be following or threatening them.

Bottom-up sensory input is too weak or missing

• Very poor eyesight / complete darkness / partial blindness / sensory deprivation

• The brain receives little meaningful data from the eyes.
  → In order to avoid a world that feels “too empty,” the brain begins to generate images from its own memories and internal patterns.

This is clearly seen in Charles Bonnet syndrome: people with severe visual loss but relatively intact cognition see vivid images of people, animals, buildings, etc.

In simple terms:

• If top-down predictions dominate,
  → the world we see becomes heavily “edited from the inside” rather than based on real input.

• If input from the eyes gradually disappears,
  → the brain refuses to let the screen of life become completely black and starts “playing its own movie.”

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5.3 Neurotransmitters — Major Neurochemical Players

Four major systems commonly appear in papers and textbooks when explaining hallucinations:

5.3.1 Dopamine — The Classic Psychosis Player

• The mesolimbic dopamine pathway (from the ventral tegmental area to the nucleus accumbens and limbic regions):
  – When dopamine activity is too high or poorly regulated, it is associated with many forms of psychosis.

One concept is that dopamine is involved in assigning “salience” (importance) to stimuli:

• If this system is abnormal, the brain gives inappropriate importance to noise or internal signals.

• Thoughts/images inside the mind may be misinterpreted as external signals from the world.

So it is not surprising that:

• Antipsychotic drugs that block D2 receptors reduce hallucinations in schizophrenia spectrum disorders.

5.3.2 Serotonin — Especially 5-HT2A and Hallucinogens

• Classic hallucinogens such as LSD and psilocybin:
  – Act as agonists or partial agonists at 5-HT2A receptors.
  – Have strong effects on visual cortex and association areas.
  → They distort visual processing and the perception of meaning.

Neurobiologically:

• Excessive stimulation of 5-HT2A disrupts the balance of cortical excitation and inhibition.

• This leads to phenomena like:
• Visual distortions
• Geometric hallucinations
• Complex vivid scenes

5.3.3 Acetylcholine — Often Impaired in Lewy Body / Parkinson’s Disease

The cholinergic system (especially projections from the basal forebrain and brainstem nuclei) has roles in:

• Attention

• Arousal

• Visual perception

In Dementia with Lewy bodies and Parkinson’s disease:

• Many cholinergic neurons are lost.

• The brain struggles to distinguish internal imagery from external stimuli.
  → Leading to classic vivid, detailed visual hallucinations.

Additionally:

• Medications with anticholinergic properties (e.g., certain allergy drugs, bladder medications, Parkinson’s medicines, some psychiatric drugs)
  – If used in high doses, especially in older adults, greatly increase the risk of delirium and visual hallucinations.

5.3.4 GABA / Glutamate — The Brain’s Brake and Accelerator

• Glutamate is the main excitatory neurotransmitter.

• GABA is the main inhibitory neurotransmitter.

If the balance between them breaks down:

• The cortex becomes hyperexcitable (firing off signals chaotically).

• In the visual cortex, this can produce both simple and complex visual hallucinations.

Examples:

• Epilepsy (especially occipital lobe epilepsy) → repeated firing of neuronal populations → flashing images, lights, patterns.

• Substances that disrupt NMDA receptors or GABAergic tone increase the likelihood of misperception.

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5.4 Other Networks — DMN, Salience Network, and Internal vs External

To judge whether “this image is coming from outside” versus “this is just in my head,” the brain uses multiple large-scale networks:

Default Mode Network (DMN)

• Active when thinking about oneself, daydreaming, imagining, recalling memories.

• If the DMN is dysregulated, the internal and external worlds can start to blend.

Salience Network (including anterior insula and dorsal anterior cingulate)

• Decides “what is important and what is noise.”

• If this network assigns salience incorrectly to internal imagery, images in the mind are treated as “real events.”

Frontoparietal Control Network

• Involved in controlling attention, working memory, and reality monitoring.

• If it fails, the ability to distinguish “what is real and what is not” is reduced.

Summarized Brain & Neurobiology:

• Problems in the visual pathway from eyes to brain → the brain generates images on its own.

• Overpowered top-down predictions / weakened bottom-up input → internal images override real-world input.

• Imbalances in dopamine, serotonin, acetylcholine, and GABA–glutamate → perception and salience networks become unstable.

• Failures in DMN, salience, and control networks → internal content is misinterpreted as external reality.

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6. Causes & Risk Factors — Causes and Risk Factors

Now we look at the diagnostic labels and risk factors behind visual hallucinations.

6.1 Psychiatric Causes — Psychiatric Disorders

Overall, auditory hallucinations are more common than visual ones in schizophrenia and related disorders, but visual hallucinations certainly occur, especially when:

• The illness is severe

• There is underlying brain pathology

• There is comorbid substance use

Main groups:

Schizophrenia spectrum disorders

• Schizophrenia

• Schizoaffective disorder

• Schizophreniform disorder

• Brief psychotic disorder

• Etc.

Visual hallucinations here:

• Often occur alongside auditory hallucinations.

• Usually accompany delusions, disorganized thinking, and negative symptoms.

• The content often aligns with themes of paranoia, religious ideas, or grandiosity.

Bipolar disorder with psychotic features

• During manic or severe depressive episodes.

• Hallucinations tend to align with mood (mood-congruent psychotic features), for example:
• In depressive episodes → images related to guilt, death, punishment
• In manic episodes → images that support grandiosity

Major depressive disorder with psychotic features

• Auditory hallucinations are more common than visual, but visual hallucinations can occur.

• Content tends to be dark, gloomy, and frightening, aligned with thoughts of worthlessness, guilt, and deserving punishment.

Psychotic disorders NOS / Other specified / Unspecified

• Cases that do not fully meet the criteria of the above categories.

• Still involve hallucinations (including visual) and delusions, but do not fit every DSM criterion perfectly.

Key point:
If we see visual hallucinations in a young or middle-aged person with other psychotic symptoms, we must strongly consider this group as the core differential.
However, before concluding that it is “purely psychiatric,” we must carefully rule out organic, substance-related, and neurological causes.

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6.2 Neurological & Neurodegenerative — Brain and Neurodegenerative Disorders

This group is particularly important in older adults and patients with clear neurological disease.

Dementia with Lewy bodies (DLB)

• One of the core clinical features is recurrent, well-formed visual hallucinations.

• Hallucinations:
• Very vivid
• Often involve people or animals with highly detailed images
• Recur in patterns, e.g., always seeing “children in the house” or “strangers sitting on the sofa.”

• Often co-occur with:
• Parkinsonism
• Cognitive fluctuations
• REM sleep behavior disorder (RBD)

Parkinson’s disease psychosis / Parkinson’s disease dementia

• Long-standing Parkinson’s disease + dopaminergic medications → high risk of visual hallucinations.

• Hallucinations:
• Often involve small people or animals.
• Some patients have good insight initially, but this may decline over time.

Alzheimer’s disease / Other dementias

• In “pure” Alzheimer’s disease, visual hallucinations are not as prominent as in DLB, but:
• In middle-to-late stages, psychosis can appear, including visual hallucinations.

• In vascular dementia, frontotemporal dementia, etc., visual hallucinations can also occur, especially when there are specific lesions.

Epilepsy (especially occipital lobe epilepsy)

• Simple visual hallucinations, such as flashing lights, zigzag patterns, colored blobs.

• Often appear as brief episodes (seconds to minutes).

• They may be followed by other seizure symptoms or post-ictal states.

Brain tumor / Structural brain lesions

• Tumors, AVMs, hemorrhages, etc., involving the visual cortex, thalamus, or brainstem can cause visual hallucinations.

• They usually come along with:
• Headache
• Focal neurological deficits (e.g., visual field loss)
• Seizures
• Cognitive or behavioral changes

Stroke in the visual pathways

• Can cause both visual loss and visual hallucinations.

• For example, lesions in the occipital lobe or parts of the thalamus can cause visual release phenomena or peduncular hallucinosis.

• Hallucinations may appear in parts of the visual field that have lost real input → the brain fills in images.

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6.3 Ophthalmologic / Sensory Deprivation — Vision Problems and Lack of Input

This is a cluster often overlooked, but common in older adults.

Severe visual impairment / blindness → Charles Bonnet syndrome

Severe vision problems such as:

• Macular degeneration

• Advanced glaucoma

• Diabetic retinopathy

• Advanced cataracts

The brain receives very little clear visual input → leading to “release hallucinations.”

Characteristics:

• Complex visual hallucinations that are very clear, colorful, and detailed.

• Typically without accompanying sounds; they do not interact with the patient in the same way as psychotic hallucinations.

• Many patients have no prior psychiatric history, and are very worried they are “going crazy,” while actually it is a brain phenomenon in low-vision states.

Other eye diseases

• The pattern of visual hallucinations may not be as classic as in Charles Bonnet, but the principle is the same:
  When visual input decreases, the probability that the brain will generate images itself increases.

Take-home for the website:
If you see an older person with poor eyesight but relatively preserved cognition who reports seeing people or animals in their house, don’t rush to dismiss them as “delusional” — consider Charles Bonnet syndrome.

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6.4 Medical / Systemic Conditions — Physical and Metabolic Illnesses

This cluster consists of “side-effects of severe body-wide problems,” where the brain is caught in the crossfire.

Delirium

Causes:

• Infections (e.g., UTI, pneumonia, sepsis)

• Organ failure (liver, kidney)

• Drug toxicity

• Metabolic disturbances (electrolyte imbalances, hypoxia, hypoglycemia, etc.)

Visual hallucinations are a common feature, combined with:

• Acute onset

• Fluctuating consciousness

• Inattention

• Disorganized thinking

High fever, encephalitis, meningitis

• High fever + neuroinfection → brain inflammation.

• Patients (especially children and older adults) may experience visual hallucinations, confused speech, agitation, and disorientation.

Endocrine / metabolic disorders

• Severe hypoglycemia → the brain is deprived of glucose.

• Liver failure → hepatic encephalopathy.

• Kidney failure → uremic encephalopathy.

• And others, such as thyroid storm, etc.

These can disrupt normal brain functioning and cause visual hallucinations and confusion.

Summary:
If visual hallucinations appear in a person with serious physical illness, always consider delirium/encephalopathy before jumping to a purely psychiatric diagnosis.

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6.5 Substance / Medication — Drugs and Medications that Affect the Brain

This is the classic cluster: anything that heavily impacts dopamine / serotonin / glutamate / GABA may trigger visual hallucinations.

Psychoactive substances / drugs of abuse

• LSD, psilocybin, mescaline → classic hallucinogens

• MDMA, methamphetamine, cocaine → stimulants that can induce psychosis

• Ketamine, PCP → NMDA receptor antagonists

• Cannabis (especially high-potency forms) can trigger psychosis in susceptible individuals

Hallucinations often involve:

• Visual distortions (overly bright colors, warped patterns)

• Geometric forms

• Complex scenes

Alcohol withdrawal (e.g., delirium tremens)

• In heavy drinkers who suddenly stop drinking:
  → tremors, sweating, rapid heart rate, confusion, and visual hallucinations such as insects crawling, shadowy figures, etc.

Medical medications

• High-dose steroids (e.g., prednisone) → steroid psychosis

• Anticholinergics (older antihistamines, some Parkinson’s drugs, bladder medications, etc.)

• Dopaminergic drugs in Parkinson’s disease (levodopa, dopamine agonists)

• Some antidepressants / antiepileptics / opioids, depending on dose and individual vulnerability

Key principle:

• If there is a clear temporal link between starting/increasing a drug/substance and the onset of hallucinations → think substance/medication-induced first.

• If symptoms improve after stopping or reducing the substance → this supports that diagnosis.

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6.6 General Risk Factors — Who Is More at Risk?

Finally, we have a set of “accelerators” or “risk boosters” that are not diseases themselves but increase the likelihood of visual hallucinations:

Older age

• Higher risk of:
• Dementia
• Delirium
• Eye diseases

• Brain networks are more fragile → hallucinations can appear more easily.

History of psychiatric illness

• Past psychosis

• Past hallucinations due to underlying psychiatric conditions
  → Indicates that the perception and salience systems have previously been destabilized.

History of neurological disease

• Parkinson’s disease, epilepsy, previous stroke, traumatic brain injury (TBI), etc.
  → The brain’s systems are already abnormal → lower tolerance to stress.

Use of substances / alcohol / brain-active medications

• Long-term, heavy, or multiple substances.
  → Increases the chance of both acute and chronic psychosis.

Sleep deprivation / chronic lack of sleep

• Research clearly shows that sleep deprivation can cause:
• Perceptual distortions
• Brief hallucinations
  especially in people who are already vulnerable.

Sensory deficits (poor vision, partial blindness)

• The less input the brain receives → the more likely it is to “project its own movie.”

Chronic stress / general brain vulnerability

• Chronic physical illness
• Malnutrition
• Deficiencies of certain vitamins (e.g., B1 in alcohol use disorder)
  → Make it harder for the brain to maintain a stable grip on reality.

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7. Treatment & Management — Treatment and Care

The main principles are: treat the underlying cause, reduce distress, and increase safety.

7.1 Initial Assessment

Assess for emergencies

• Is there delirium? Is the patient drowsy, confused, febrile, with abnormal vital signs?

• Is there a risk of self-harm or harm to others?

Prepare a workup

• Detailed history: onset time, nature of hallucinations, triggers, medications/substances used, medical history

• Physical examination + neurological evaluation

• Appropriate lab tests and imaging (brain CT/MRI, EEG, blood tests, etc.)

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7.2 Treating the Underlying Cause

Psychotic disorders (e.g., schizophrenia)
– Use antipsychotic medications (dopamine D2 blockers / atypical antipsychotics) according to guidelines.
– Combine with psychoeducation, CBT for psychosis, and social support.

Delirium
– Identify and treat underlying causes (infection, metabolic abnormalities, drugs, withdrawal, etc.).
– Adjust the environment (lighting, noise, sleep-wake cycle, orienting cues).
– Use low-dose antipsychotics in some cases with severe agitation or safety risks.

Dementia with Lewy bodies / Parkinson’s psychosis
– Adjust dopaminergic medications.
– Use appropriate antipsychotics with caution regarding side effects (e.g., quetiapine, clozapine).
– Consider cholinesterase inhibitors in some cases.

Substance-induced hallucinations
– Stop, reduce, or detox from the relevant substances or medications.
– Provide safety monitoring and supportive care.

Charles Bonnet syndrome / low-vision hallucinations
– Explain to the patient that this is a phenomenon arising from poor vision + the brain filling in images.
– Optimize environmental lighting, reduce isolation, use glasses or low-vision aids.
– In some cases, consider low-dose antipsychotics or other medications depending on the individual case.

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7.3 Non-Pharmacological Management

Psychoeducation
– Explain the mechanisms in simple, understandable language to reduce fear and shame.
– Teach families not to argue aggressively that “it’s not real” while the person is terrified; instead, focus on safety and staying with them.

Coping strategies (depending on the case)
– Change viewing angle, turn on lights, switch activities, close eyes temporarily, listen to music, call someone, etc.

Environmental adjustments
– Ensure adequate lighting, reduce patterns that promote illusions, use familiar objects to help orient.

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7.4 Safety & Monitoring

• Evaluate risks of self-harm, wandering, falls, and aggression.

• Plan long-term follow-up if psychotic disorders or dementia are suspected.

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8. Notes — Additional Points / Cautions

• Pure visual hallucinations without auditory hallucinations
  – In older adults → always consider organic causes such as delirium, dementia, structural lesions.
  – In younger people with simultaneous auditory hallucinations or delusions → think of primary psychosis.

• Content of hallucinations can guide diagnosis somewhat, but not 100%
  – Vivid, detailed, recurrent visual hallucinations + parkinsonism + cognitive fluctuations → suggest DLB.
  – Simple flashes or zigzag shapes → suggest migraine aura or occipital epilepsy.

• Always ask about medications and substances
  – People often do not volunteer this information unless asked clearly and directly.

• Not the same as “seeing spirits” in cultural contexts
  – When writing articles, it is important to separate “cultural/religious experiences” from clinical hallucinations.

• Many patients fear being labeled “crazy,” so they hide symptoms
  – This leads to delayed diagnosis. Articles should emphasize stigma reduction.

Read Schizophrenia

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Reference

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th ed., Text Revision (DSM-5-TR). Sections: Schizophrenia Spectrum and Other Psychotic Disorders; Delirium; Major and Mild Neurocognitive Disorders. NCBI+1

American Psychiatric Association. What is Schizophrenia? (Patient & Families resource, psychiatry.org). Explains psychosis, hallucinations, delusions, and insight in schizophrenia. American Psychiatric Association

MSD Manual Professional Version. Schizophrenia – Psychiatric Disorders. Provides an overview of psychosis, hallucinations, delusions, and basic neurobiology. MSD Manuals

Taylor J-P, et al. Visual hallucinations in dementia with Lewy bodies. International Journal of Geriatric Psychiatry. 2011. A detailed review of brain mechanisms and clinical features of visual hallucinations in DLB (considered a classic review). PMC

Devenyi R, et al. Visual dysfunction in dementia with Lewy bodies. Current Neurology and Neuroscience Reports. 2024. Reviews visual hallucinations and visual network dysfunction in DLB in an updated form. SpringerLink

Weil R, et al. Hallucinations in Parkinson’s disease: new insights into mechanisms and treatment. Journal of Neurology, Neurosurgery & Psychiatry / or Brain review on PD psychosis and visual hallucinations (including the role of serotonin 5-HT2A and drugs such as pimavanserin). PMC+1

Parkinson’s Foundation. Hallucinations and Delusions in Parkinson’s Disease. A resource for patients and families explaining the relationship between PD, dopaminergic medications, and visual hallucinations. Parkinson’s Foundation

Rojas LC, et al. Charles Bonnet Syndrome. StatPearls [Internet]. Updated 2023. Reviews the mechanism of “release hallucinations” in people with visual impairment (complex visual hallucinations with generally good insight). NCBI

Subhi Y, et al. Prevalence of Charles Bonnet syndrome in patients with low vision: systematic review. Annals of Eye Science. 2022. Summarizes the prevalence and risk factors of CBS in people with severe visual impairment. aes.amegroups.org

Schadlu AP, et al. Charles Bonnet syndrome: a review. Current Opinion in Ophthalmology. 2009. A classic review of clinical features and theoretical mechanisms of CBS. PubMed

Firbank MJ, et al. Functional connectivity in Lewy body disease with visual hallucinations. European Journal of Neurology. 2024. A recent study focusing on dysfunctional connectivity of visual and attentional networks in LBD with visual hallucinations. Wiley Online Library

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