Hallucinations

1. Overview — What are Hallucinations?

Hallucinations are “perceptual experiences that occur in the mind as if they are real, but in the complete absence of any external stimulus.” They are experiences in which the brain generates images, sounds, smells, tastes, or bodily sensations entirely on its own, as if they were real-world events, even though there is no stimulus coming from the outside world at all.Their realism can be so intense that the person genuinely believes, “It is happening right in front of me,” even though people around them do not see or hear anything. This is not imagination or daydreaming; it is a full-blown perception with a sensory quality comparable to everyday real experiences, such as hearing a person speak clearly right next to one’s ear, or seeing someone walking around the room when in fact nobody is there.

Hallucinations are a symptom, not a stand-alone disease. Importantly, they can appear in many different illnesses or conditions: from schizophrenia, to hypoglycemia and certain seizure disorders, to substance use and withdrawal, and even in chronic stress and severe sleep deprivation. What these very different conditions have in common is that “the sensory systems are being abnormally activated.” The brain misinterprets noise in neural activity as meaningful information, resulting in false perceptions that are extremely vivid.

Hallucinations can be divided into five main types according to the sensory modality:

• Auditory (hearing voices or sounds): the most common type, especially in schizophrenia.

• Visual (seeing things): often found in delirium, substance use, and neurodegenerative diseases.

• Olfactory (smell): for example, smelling burning, gas, or something rotten, often associated with temporal lobe pathology.

• Gustatory (taste): rare but can be linked to certain types of seizures.

• Tactile / Somatic (touch or bodily sensations): such as feeling insects crawling on or under the skin, or feeling as though someone is touching the body.

Crucially, hallucinations are different from imagination, drifting thoughts, or “pictures in the mind,” because the person experiences them as if they are “coming from outside” and often believes they are genuinely happening. They must also be distinguished from illusions (misinterpretations of real stimuli), such as seeing a coat hanging and thinking it is a person standing there, which is not a true hallucination.

Although this symptom is most strongly associated with psychotic disorders, hallucinations can also occur in otherwise healthy individuals under certain conditions, such as during the transition into sleep (hypnagogic) or the transition out of sleep (hypnopompic). These are experiences many people have encountered without realizing, and they are not considered disorders unless they cause significant distress or impair functioning.

Hallucinations are therefore “signals from the brain” indicating that the perceptual processing system is operating in an abnormal mode. This may be related to excessively elevated dopamine, dysfunction in language processing networks, degeneration of visual circuits, imbalance in the glutamate–GABA system, or increased neural noise due to stress and sleep deprivation.

For writing or content on mental health:
Hallucinations are one of the most confusing symptoms for the public, because society often interprets them as “ghosts” or being “possessed” or “mentally cursed,” when in reality they are neurobiological phenomena supported by extensive research. Explaining them in a structured way is therefore crucial, from clinical, neuroscience, and psychological perspectives, so that people understand that this symptom is not the patient’s fault and should not be stigmatized or seen only as something supernatural.

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2. Core Symptoms — The Core Features of Hallucinations

This section is the “skeleton structure” that defines what makes an experience a true hallucination—as opposed to simply overthinking, imagining, or misinterpreting something that actually exists.

2.1 Perception-like experience — An experience that feels like real perception

The most important starting point is the quality of the experience.

The person does not feel as though “I am imagining this,” but rather as though they are truly hearing/seeing/feeling something.

Examples:

• Hearing a man’s voice clearly insulting them, as if he is standing right by their ear, but when they turn around, nobody is there.

• Sitting on the bed and seeing a little girl standing in the corner of the room, with a clearly detailed face and clothes, yet no one else can see her.

• Feeling as if insects are crawling under the skin or walking along the arm, even though there is nothing visible.

What distinguishes hallucinations from “thoughts/images in the head” is that:

• They typically occur spontaneously, without intention, and the person often says, “It just came by itself,” not that they deliberately imagined it.

• They have sensory quality, such as pitch, volume, and distance for sounds; color, light, and shadow for images; or specific textures and temperatures for bodily sensations.

• Some people say things like:

“It feels completely real. The only difference is that nobody else can see or hear it.”

Key point for clinical work and content:
When clinicians or writers explain this, they must emphasize that hallucinations are not just overthinking or “getting carried away with imagination.” They are percepts created by the brain as if responding to real stimuli, which is profoundly confusing and distressing for the person experiencing them, making them wonder, “What is happening to my brain?”

2.2 No external stimulus — There is no real stimulus present

The technical heart of the definition is: perception in the absence of external stimulus.

There is no actual sound, no real person standing there, no real insect on the skin.

Yet the brain behaves as if it is receiving input from the outside world.

To contrast this clearly:

• If someone is sitting in a dark room and a coat is hanging on the door, and they glance at it and think it’s a person → this is an illusion (a misinterpretation of a real stimulus).

• But if they are sitting in an empty, bare room with blank walls and nothing in it, and they see a person leaning against the wall → this is a visual hallucination.

The crucial difference:

• Illusion = there is something real (a lamp, hanging clothes, the sound of a car), but the brain interprets it incorrectly.

• Hallucination = there is nothing there at all, and the brain creates the object/event entirely by itself.

Highlighting this point is important both for diagnosis and for writing, because many people casually lump all episodes of “seeing/hearing something wrong” together as hallucinations, which is not clinically accurate.

2.3 Sense of reality / conviction — The feeling that “this is real,” or almost real

Another core element that makes hallucinations powerful and terrifying is their sense of reality.

Many people who experience them believe that:

• “It is definitely real.”
• Not merely, “It feels real, but I know it’s probably my imagination.”
• Some even argue with doctors or family members:

“You don’t hear it, but I can hear it clearly.”

In reality, there are several levels:

No insight (100% belief)

• They see/hear the hallucination as a genuinely occurring event in the world.
• If it is a voice commanding them to “jump down,” they might obey, believing it to be an order from a powerful force or entity that controls their life.

Partial insight (feels real, but they suspect it may be abnormal)

Common statements include:

• “I know it’s probably in my head… but when it happens, it feels so real.”
• “There must be something wrong with my brain, because it’s like there’s someone talking right next to me.”

This group often responds better to explanation and psychological therapies, because there is still room for reality testing.

Good insight (recognizing that it is a symptom of illness)

These are cases that have been under treatment for some time. The symptoms may still appear, but the person is now able to label them, for example:

• “Okay, this is a hallucinated voice. I don’t have to believe it.”

This is a medium-term treatment goal: not necessarily making the voices disappear entirely, but helping the person distinguish what is a symptom and avoid following its commands.

Key point:
The degree of sense of reality + insight is directly linked to:

• The risk of self-harm or harming others (especially with command hallucinations).
• Treatment adherence.
• Planning psychological interventions—for example, whether medication alone might be enough, or whether to combine it with CBT, psychoeducation, family therapy, etc.

2.4 Distress & impairment — Suffering and disruption of daily life

Hallucinations are not just “strange phenomena”; in most cases, they cause severe suffering.

In terms of distress:

• Abusive/self-critical voices:
• “You are worthless.”
• “Nobody loves you.”
• “You should kill yourself.”

• Threatening voices:
• “They’re going to kill you tonight.”
• “Don’t leave the room, or they will find you.”

• Frightening visual hallucinations:
• Seeing disfigured faces, severely deformed bodies, blood, or dead bodies in various places.

• Tactile hallucinations:
• Feeling living creatures inside the body, feeling grabbed, stroked, stabbed, or shocked, when nothing is actually happening.

These can lead to:

• Chronic anxiety, panic attacks, and constant hypervigilance.
• Inability to sleep, needing to keep the lights or TV on all night.
• Severe depression due to being “bullied” by the voices in the head continuously.

In terms of functioning (impairment):

• Work/study:
• It is impossible to both listen to hallucinated voices and focus on tasks at the same time.
• In meetings, the person may feel colleagues are talking about them or mocking them (even when they aren’t).
• Relationships:
• They may distrust people around them because the voices say that others intend to harm them.
• They may withdraw from friends and family for fear of being seen as “crazy.”
• Basic daily living:
• They may be too afraid to leave the house because they fear the voices or images will follow them everywhere.
• They may be unwilling to go to the bathroom or bedroom alone.

In clinical assessment, it is not enough to ask, “Do you have hallucinations?”
It is essential to also ask:

• How much distress do they cause? (0–10)
• What aspects of daily life do they interfere with?
• Have there been times when you almost harmed yourself or others because you followed what the voices said?

2.5 Relation with other symptoms — How hallucinations link with other symptoms

Hallucinations do not typically appear in isolation. They usually come as part of a “package” of symptoms in psychosis, mood disorders, and trauma-related conditions.

2.5.1 Connection with delusions

Examples:

• Hearing a voice say, “Someone has installed cameras in your room” → then developing a delusion of being spied on.
• Hearing a voice say, “They’re going to kill you” → evolving into a persecutory delusion that someone is hunting them.

In terms of brain models:

• Hallucination = an abnormal sensory signal.
• Delusion = a story or belief the brain constructs to explain that abnormal signal.

Therefore, hallucinations often become the starting point for a distorted narrative.

2.5.2 Connection with mood (mood congruence / incongruence)

In severe depression:

• Voices are often mood-congruent, such as insulting, demeaning, or encouraging suicide.
• This greatly increases suicidal risk.

In mania/hypomania:

• Voices may praise the person, magnify their sense of greatness, or tell them they have special powers.
• Content is often grandiose, religious, or “special mission” themed.

This relationship helps differentiate:

• Psychotic depression vs. schizophrenia
• Bipolar with psychotic features vs. primary psychotic disorders

2.5.3 Connection with cognitive symptoms & disorganization

People with intense, frequent hallucinations often have:

• Easily disrupted attention.
• Difficulty organizing thoughts, because the brain is constantly trying to manage “other voices.”

In schizophrenia, for example, one often sees:

• Disorganized speech.
• Thought derailment or loosening of associations.

All of this reduces quality of life far more than having hallucinations alone.

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3. Diagnostic Criteria — How hallucinations are diagnosed

This section looks at how clinicians think when they encounter someone with hallucinations, and what criteria they use to determine which disorder the symptom belongs to—and what it is not.

Remember clearly:
👉 Hallucinations = a symptom
👉 Diagnosis = a disorder, such as Schizophrenia, Bipolar I with psychotic features, MDD with psychotic features, Delirium, Substance-induced psychotic disorder, etc.

3.1 The clarity of hallucinations — Modality, frequency, continuity

When taking history, clinicians ask in considerable detail, for example:

Modality

• What do you hear? One voice or multiple? Male or female? Do you recognize them?
• What do you see? People? Shadows? Animals? Light? Distorted images?
• What do you feel on your skin or inside your body?
• Do you smell or taste anything unusual?

Vividness

• How loud/clear is it compared with normal sounds?
• How detailed are the images? Colors? Shadows? Movement?
• Are the bodily sensations clear enough to feel real pain or itching?

Temporal pattern (frequency & duration)

• How often do they occur:
• Once a month, once a week, once a day, once an hour, or almost constantly?

• How long does each episode last:
• A brief flash of 2–3 seconds, several minutes, or hours?

• Are there triggers:
• Severe stress, sleep deprivation, substance use, darkness, being alone, etc.?

Longitudinal pattern

• Did it start only within the last few weeks or months, or has it been present for years?
• At what age did it first appear? (Very important, because schizophrenia often begins in late adolescence to early adulthood.)

All of this is used to:

• Assess which diagnostic picture it fits best.
• Distinguish medical conditions, such as delirium (acute onset) vs. dementia (gradual onset).
• Plan further tests (blood work, brain imaging, EEG, etc.).

3.2 Insight — Awareness that it is a symptom of the brain/illness

Insight indicates:

• How likely the person is to cooperate with treatment.
• How likely they are to follow the commands of voices or visual hallucinations.

Questions assessing insight often include:

• “What do you think these voices/images are?”
• “What do you think causes them?”
• “If your friend had the same experiences, would you think they are ill?”

Insight can be roughly divided into:

No Insight (Psychotic level)

• They believe everything is real without doubt.
• They do not accept that it is an illness and do not want treatment, believing they are not ill.
• The risk is very high with command hallucinations.

Partial Insight

• They know it is “abnormal,” but it still feels very real.
• They might say, “I know there probably isn’t anyone there, but in that moment it felt completely real.”
• This group is especially suited for CBTp and psychoeducation.

Good Insight

• They clearly recognize that this is a symptom of illness/brain dysfunction.
• They can describe:
• “When my symptoms flare up, I hear voices like this and that, but now I know it’s because of my condition.”

They may still suffer, but have higher meta-awareness.

In DSM/ICD, some diagnoses specify a specifier such as “with good/fair/poor/absent insight,” which affects prognosis and treatment planning.

3.3 The context of the primary disorder — Which diagnostic frame do the hallucinations fit into?

In diagnostic terms, clinicians do not only ask whether hallucinations are present; they also ask:

“Which disorder do they best fit with?”

Broad categories:

3.3.1 Schizophrenia

Hallucinations—especially auditory hallucinations—are one of the core symptoms in Criterion A for schizophrenia, along with:

• Delusions
• Disorganized speech
• Grossly disorganized or catatonic behavior
• Negative symptoms (avolition, alogia, flat affect, etc.)

Key criteria:

• At least one month of “active phase” symptoms (e.g., delusions, hallucinations, disorganized speech).
• The overall course of the disorder lasting ≥ 6 months (including prodromal and residual phases).
• Clear impairment in work, relationships, or self-care.

If hallucinations appear in this pattern, combined with onset in late adolescence or early adulthood, clinicians will first consider the schizophrenia spectrum.

3.3.2 Schizoaffective / Bipolar with psychotic features / MDD with psychotic features

Here the question is whether hallucinations:

• Occur within the context of clear mood episodes (e.g., severe depression, mania) or not.
• Are mood-congruent or not (whether their content aligns with the person’s mood).

Overall picture:

• Bipolar with psychotic features
• Hallucinations appear only during manic or depressive episodes.
• When mood returns to euthymia, psychosis resolves.

• MDD with psychotic features
• Hallucinations occur only during severe depressive episodes.

• Schizoaffective disorder
• There are mood episodes (mania/depression) plus psychotic symptoms that persist even when there is no mood episode.

Differentiating these can be very complex in real practice, but the key question is:

• “Have there been periods when hallucinations or delusions were present while your mood was not abnormal (not particularly depressed or elevated)?”

If yes → more toward schizophrenia/schizoaffective.
If no → psychosis is tightly linked to mood → mood disorder with psychotic features.

3.3.3 Delirium / Dementia / Neurocognitive disorders

If hallucinations occur along with:

• Confusion.
• Disturbances in orientation to time/place/person.
• Fluctuating levels of consciousness (sometimes clear, sometimes very confused).

Delirium will be suspected first, especially in elderly, critically ill patients, or ICU settings.

• Delirium
• Acute onset over days to weeks.
• Visual hallucinations are common (seeing insects, strangers, animals).

• Dementia / Lewy body / Parkinson’s disease
• Visual hallucinations are a prominent feature.
• The person often sees people or small animals walking around the house and outdoors.
• This occurs along with cognitive decline and motor symptoms.

3.3.4 Substance / Medication-Induced Psychotic Disorder

If hallucinations:

• Begin soon after taking drugs/medications.

• Intensify during intoxication or withdrawal.

• Follow a clear pattern with specific substances, for example:
• Amphetamine, meth, cocaine → paranoid delusions + visual/tactile hallucinations.
• Alcohol withdrawal (delirium tremens) → seeing small animals or insects crawling on the walls.
• LSD, psilocybin → visual distortions, altered colors, unusual patterns.

Clinicians will map out a timeline:

• What substance was used, when, and how much.
• When the symptoms started relative to use or cessation.

They will then distinguish between:

• Substance-induced psychotic disorder, and
• A primary psychotic disorder where substances act as a trigger but are not the root cause.

3.4 Rule out conditions that “seem like hearing/seeing” but are not true hallucinations

This step is often overlooked in general articles but is extremely important clinically and for credible writing: we must differentiate other conditions that resemble hallucinations but are not true hallucinations.

3.4.1 Illusions

There is a real stimulus, but the brain misinterprets it.

Examples:

• Seeing a coat’s shadow at night and thinking it is a person standing there.
• Hearing dripping water and thinking it is footsteps.

They often occur:

• In low light.
• In strange environments.
• When extremely tired or stressed.

Healthy people experience illusions frequently, and they are not considered psychosis.

3.4.2 Hypnagogic / Hypnopompic phenomena

• Hypnagogic = during the transition into sleep.
• Hypnopompic = during the transition out of sleep.

Many people:

• Hear their name being called.
• See fleeting images as if someone walked past.
• Feel as if they are falling from a height.

If these experiences occur only in these phases and do not impair daily life, they are considered a normal variant, not a disorder.

3.4.3 Intrusive thoughts / imagery

In OCD, PTSD, and anxiety disorders, some people have intrusive images or thoughts that are extremely frightening, such as:

• Suddenly seeing, in the mind’s eye, an image of stabbing someone.
• Imagining accidents or the death of loved ones over and over.

But they usually know:

• “These are images in my head.”
• They do not feel that the voices or images are “coming from outside.”

This distinction is critical, because if we fail to separate them, we might misdiagnose psychosis when the person actually has OCD or a trauma-related condition.

3.4.4 Cultural beliefs & spiritual experiences

In some cultures, people report experiences such as “hearing the voice of a sacred being” or “seeing ghosts/spirits.”

If:

• The experience does not cause personal distress.
• It does not impair functioning.
• It is consistent with the beliefs of that culture.

→ Many clinical guidelines do not immediately label such experiences as illness.

However, they become a clinical problem when:

• They cause significant distress.
• There is risk of self-harm or harming others.
• Other clear symptoms of psychotic disorders are present alongside them.

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4. Subtypes or Specifiers — Types and Forms of Hallucinations

The main dimensions are: sensory modality, content, and clinical quality.

4.1 Classification by modality

Auditory hallucinations (hearing voices)

• The most common type in schizophrenia.

• Possible forms:
• Voices talking about the person in the third person (third-person commentary).
• Voices talking among themselves (voices conversing with each other).
• Command hallucinations (voices giving orders) — high risk for self-harm or violence.

• The voices are often perceived as coming from “outside the head” (though some people feel them inside the head).

Visual hallucinations (seeing things)

• Seeing people, beings, shadows, flashes of light, or strange shapes.
• In psychotic disorders, they often involve clear images of people or living creatures.
• In delirium or substance-induced states, they may be fleeting, fast-moving images or overlapping, shifting visual scenes.

Olfactory hallucinations (smell)

• Smelling something strange, like burning, gas, or rotting odors.
• These raise suspicion of neurological conditions, such as temporal lobe epilepsy or certain brain tumors.
• Some patients find them intolerable, leading to high levels of anxiety.

Gustatory hallucinations (taste)

• A strange taste on the tongue (bitter, metallic, spoiled) despite eating nothing.
• Rare, but often associated with other symptoms such as olfactory hallucinations or epilepsy.

Tactile / Somatic hallucinations (touch/bodily sensations)

• Feeling touched, grabbed, electrically shocked, or feeling insects crawling under the skin (formication).
• Seen in psychotic disorders, substance use (e.g., cocaine, amphetamine), alcohol withdrawal, and sometimes dermatological conditions combined with anxiety or delusional beliefs.

4.2 Classification by content and form

Second-person vs. third-person voices

• Second-person: “You’re stupid,” “Jump now.” → high risk for self-harm.
• Third-person: “He is walking to the bathroom,” “He can’t be trusted.” → often linked with paranoia.

Supportive vs. hostile voices

• Some people hear encouraging or comforting voices, but many hear critical, insulting, or cursing voices.
• Hostile voices are associated with depression, trauma, and low self-esteem.

Commentary vs. dialogues

• Commentary = narrating the person’s life, as if someone is reading their script.
• Dialogues = multiple voices talking about the person → a classic feature of schizophrenia.

4.3 Classification by level of insight

True psychotic hallucinations with no insight

• Believed to be 100% real.
• The person may argue or interact with the voices, or follow their commands.

Pseudo-hallucinations / hallucinatory experiences with partial insight

• The person knows it is strange and probably coming from the brain, but it still feels realistic.
• Seen in some cases of OCD, PTSD, and dissociative phenomena.

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5. Brain & Neurobiology — The Brain and Neural Mechanisms of Hallucinations

From a neuroscience perspective, hallucinations are the result of the reality-monitoring system malfunctioning at both the network level (network-level dysfunction) and the molecular level (neurochemical dysregulation). It is no longer adequate to explain them simply as “high dopamine,” as older models did. Currently, four major pillars are widely accepted:

• Predictive coding gone wrong
• Aberrant salience from dopamine
• Errors in inner speech and language circuits
• Excitatory–inhibitory imbalance (glutamate–GABA) + network disconnection

Below is the upgraded, detailed version:

5.1 Predictive Coding — The brain as a “world-prediction machine” that is mis-tuned

The most recent models in cognitive neuroscience propose:

The brain does not passively wait for information from the world.
It “predicts the world first” and then compares those predictions with real data.

Process:

• The brain generates predictions (prior expectations) about what it should hear/see at any given moment.
• When sensory information arrives, it computes prediction error—the difference between what was expected and what actually occurred.
• The brain then updates its predictions to become more accurate over time.

In hallucinations, this system malfunctions in three main ways:

A) Overly strong priors → the brain trusts its predictions more than reality

• For example, inner speech (the internal voice in one’s mind) is misinterpreted as an external voice, because the brain is too convinced that there must be an external source.
• In auditory hallucinations, the brain assigns excessive weight to its predictions, and so creates a voice even when there is no real auditory input.

B) Misinterpretation of prediction error

• In healthy brains, incorrect predictions are corrected over time.
• In psychosis, instead of updating its priors, the brain “amplifies the abnormality,” leading to increasingly distorted perception.

C) Attenuated sensory input

• If incoming sensory data are reduced (e.g., due to sleep deprivation, severe stress, or impaired sensory gating),
  → the brain “fills in the gaps” to maintain a coherent experience of the world.

Thus:

• Severe sleep deprivation → visual hallucinations.
• Prolonged isolation in a quiet room → strange auditory and tactile experiences.
• Schizophrenia → hearing voices telling the person to do things, even without actual stimuli.

5.2 Dopamine Dysregulation — The dopamine system assigning “excessive meaning” to meaningless stimuli

The Aberrant Salience Hypothesis by Kapur is highly influential and still heavily used:

Dopamine is not only associated with “pleasure.”
It is a system that tags stimuli with importance—deciding what deserves attention and what matters to the brain.

In psychosis:

• The mesolimbic dopamine pathway (VTA → Nucleus Accumbens) is overactive.
• Stimuli that should be neutral are assigned abnormal significance.

Consequences:

• Ordinary thoughts feel as though they carry “deep, special meaning.”
• Inner speech is perceived as an external voice.
• Spontaneous thoughts are interpreted as messages from other people or supernatural forces.

In short:

• Elevated dopamine → positive symptoms (hallucinations + delusions).
• But dopamine is not the sole cause; it interacts with disrupted predictive coding.

5.3 Auditory Hallucinations & Language Circuits — The brain mislabeling “its own voice” as someone else’s

Research shows that during auditory hallucinations:

• The brain activates similar circuits as when hearing real sounds.

Regions that become active include:

• Primary auditory cortex (Heschl’s gyrus)
• Superior temporal gyrus (sound processing)
• Wernicke’s area (language comprehension)
• Broca’s area (speech production / inner speech)
• Default Mode Network (DMN) (internal mentation)

A key hypothesis:

Hallucinated voices = inner speech
that the brain fails to recognize as its own.

Because the self-monitoring system is damaged:

• Thoughts in the mind → are misinterpreted as other people’s voices.
• The thought “I am worthless” → is heard as a distinct voice harshly insulting the person.
• Past memories → erupt as vivid voices or images that feel current.

This system may break down due to:

• Prefrontal cortex abnormalities (reduced reality-checking).
• Hyperconnectivity in the DMN.
• Hyperactivity in the auditory cortex.

This explains why hallucinated voices feel “so real” even in the absence of any external source.

5.4 Glutamate–GABA Imbalance — Overactive excitation / weakened inhibition

The brain needs a balance between the excitatory system (glutamate) and the inhibitory system (GABA) for perception to work smoothly.

In hallucinations:

• Glutamate is excessively high / firing activity is overactive.
• GABA is too low / inhibition is weakened.
• The brain cannot filter signals properly (sensory gating impairment).

Consequences:

• Neural noise in the brain increases.
• Meaningless signals are processed as meaningful information.
• The brain tries to weave this noise into coherent “stories” → delusions.
• External sensory information mixes with internal stimuli → hallucinations.

This explains why:

• Ketamine, which affects the NMDA–glutamate system, can induce hallucinations.
• Schizophrenia is linked to NMDA receptor hypofunction.

5.5 Structural & Functional Abnormalities — Problems in brain structure and connectivity

Studies have found multiple abnormalities:

Temporal Lobe Abnormalities

• Especially in the Superior Temporal Gyrus (STG) and Planum Temporale.
• These areas are involved in hearing, sound separation, and localizing where sounds come from.

Prefrontal Cortex Deficits

• Reduced capacity for reality-testing and self-monitoring.
• Difficulty distinguishing whether voices/thoughts originate internally or externally.

Hippocampus & Limbic System

• Abnormalities in memory integration cause past images to intrude into present perception.

Thalamus Dysfunction

• The thalamus acts as the “gateway” for sensory information.
• If its gating is faulty, incorrect signals may be sent to the cortex, resulting in non-existent images or sounds.

Cholinergic Dysfunction (especially in Lewy Body Dementia)

• Strongly associated with prominent visual hallucinations.

In summary:
Hallucinations = simultaneous dysfunction in multiple systems.
They do not arise from a single cause, but from a combination of dopamine, glutamate/GABA imbalance, network connectivity problems, and predictive coding failure.

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6. Causes & Risk Factors — Causes and Contributing Factors

Hallucinations are not caused by “dopamine” alone; they arise from an interplay of:

• Biology
• Genetics
• Developmental factors
• Psychological and environmental factors
• Substance use
• Neurological diseases
• Chronic stress
• Sleep disruption

Below is the comprehensive, in-depth version:

6.1 Biological Factors — Genetics & Brain Chemistry

A) Genetics

• Having a parent with schizophrenia → risk increases about tenfold.
• Identical twins → very high concordance rates.
• Associated genes include:
• COMT
• DISC1
• NRG1
• GRIN2A (involved in glutamate NMDA receptors)

There is no single “hallucination gene”; it is a polygenic risk plus environmental factors.

B) Neurochemical Dysregulation

1. Dopamine
→ Aberrant salience, misattribution, and positive symptoms.

2. Glutamate (NMDA hypofunction)
→ Impaired sensory gating → abnormal signals constantly intruding.

3. GABA deficits
→ Insufficient inhibition → chaotic neural firing.

4. Serotonin
→ Involved in hallucinations induced by LSD/psilocybin (via 5-HT2A receptors).

6.2 Psychiatric Disorders — Mental disorders associated with hallucinations

1. Schizophrenia Spectrum

• Auditory hallucinations occur in 60–80%.
• Negative symptoms and cognitive deficits are often present.
• Hallucinations are chronic and not tied strictly to mood.

2. Major Depressive Disorder with Psychotic Features

• Content typically includes harsh, demeaning voices, often telling the person to kill themselves (mood-congruent).
• Hallucinations occur only during depressive episodes.

3. Bipolar I Disorder with Psychotic Features

• Mania → grandiose hallucinations.
• Depression → critical or insulting hallucinations.

4. PTSD / Dissociative Disorders

• Some people “hear the abuser’s voice from the past.”
• Or repeatedly see images of traumatic events.
• Often pseudo-hallucinations (some degree of insight remains).

6.3 Substance-induced Hallucinations — Hallucinations from drugs and medications

A) Stimulants (Amphetamine, Meth, Cocaine)

• Visual and tactile hallucinations.
• Paranoid delusions.
• High severity and risk due to impulsivity.

B) Hallucinogens (LSD, Psilocybin, Mescaline, MDMA)

• Visual distortions.
• Synesthesia.
• Altered perception of time, size, and color.

C) Alcohol Withdrawal (Delirium Tremens)

• Seeing small animals or insects crawling on walls.
• Accompanied by confusion, palpitations, and sweating.

D) Marijuana (High-THC)

• May trigger psychosis in individuals with genetic vulnerability.
• Can cause auditory hallucinations in some users.

E) Certain Medications

• Steroids.
• Dopaminergic drugs (used in Parkinson’s disease).
• Anticholinergics.
• Some sleep medications.

6.4 Neurological & Medical Conditions — Brain and physical illnesses

1. Temporal Lobe Epilepsy

• Olfactory hallucinations (burning, rotten smells).
• Visual distortions.
• Extremely intense déjà vu.

2. Parkinson’s Disease

• Prominent visual hallucinations.
• Seeing people or small animals moving around.
• Linked with degeneration of cholinergic systems.

3. Lewy Body Dementia

• Hallucinations are a hallmark.
• Occur earlier than in Alzheimer’s disease.
• People often see clear images of people, children, or animals.

4. Brain tumors, stroke, encephalitis

• If they affect sensory cortex or thalamus → hallucinations can appear immediately.

5. Delirium

• Acute onset.
• Fluctuating course (better–worse–better).
• Visual hallucinations are prominent.

6.5 Psychological & Environmental Factors — Psychological and social accelerators

A) Trauma (especially childhood trauma)

Research shows:

• Children who experience physical, sexual, or emotional abuse
  → have a significantly higher risk of hallucinations in adulthood.

• The brain develops under conditions of hypervigilance, causing threat-detection systems to become oversensitive.

B) Severe Stress

• Chronic elevated cortisol damages the hippocampus.
• This makes brain networks hyperactive and prone to misinterpreting stimuli.

C) Sleep Deprivation

• 24–72 hours of insufficient sleep → hallucinated voices may start.
• The body enters a “dream intruding into wakefulness” mode,
  → where dream content spills into waking consciousness.

D) Isolation / Sensory Deprivation

• Being in extremely quiet, dark, or isolated environments for long periods
  → the brain generates hallucinations to “fill in the gaps.”

E) Cultural Interpretations

• Some societies interpret these experiences as “a ghost entering dreams” or “a deity communicating.”
• This can obscure the person’s recognition that they might need help.
• Certain cultures have hallucination patterns specific to their belief systems.

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7. Treatment & Management — Treatment and Care

Managing hallucinations must begin with the question: “What underlying disorder is causing them?” because treatment follows the root condition.

7.1 Assessment & Differential diagnosis

• Detailed history-taking
• When did the hallucinations start? How often? In which modality?
• What is the content, how terrifying or distressing is it, and are there any commands?
• Are there thoughts or plans of harming self or others?

• Evaluation for organic / neurological causes
• Physical examination, neurological examination, and possibly blood tests, brain imaging, EEG, etc., as appropriate.

• Assessment of substance use
• Alcohol, illicit drugs, and prescribed medications.

7.2 Pharmacological treatment (medications)

Antipsychotics

• Mainly dopamine D2 receptor antagonists / partial agonists.
• First-line in schizophrenia, schizoaffective disorder, bipolar disorder with psychotic features, and MDD with psychotic features.
• They help reduce the frequency and intensity of hallucinations.
• They are divided into first-generation (typical) and second-generation (atypical) antipsychotics, but real-world choice depends on patient profile, side effects, and clinical guidelines.

Adjusting other medications that trigger symptoms

• If hallucinations are caused by other medications (e.g., antiparkinsonian drugs, steroids, etc.), clinicians may reduce or switch those drugs.

Treating underlying medical causes

• Delirium, metabolic disturbances, seizures, and brain lesions must be treated at their root for hallucinations to remit.

7.3 Psychological & psychosocial interventions

CBT for psychosis (CBTp)

Helps patients:

• Understand the nature of hallucinations.
• Challenge related beliefs (e.g., “This voice is a divine command” → examine evidence and alternative explanations).
• Develop coping strategies, such as not arguing with the voice, using distraction techniques, and practicing grounding.

Acceptance & Commitment / Mindfulness-based approaches

• Shift the focus from “I must stop the voices” → to “I can learn to live with the voices without following their commands or defining myself by them.”

Trauma-focused therapies

• In cases where hallucinations are linked to trauma (e.g., hearing an abuser’s voice from the past).
• Healing the trauma may reduce the distress associated with the hallucinations.

Family psychoeducation & support

• Educate family and close others about what hallucinations are, correcting misconceptions like “it’s just overthinking” or “you’re imagining things.”
• Reduce stigma and encourage continuous treatment and support.

7.4 Everyday coping strategies

• Playing music or podcasts to partially mask the voices.
• Calling a friend or trusted person when the voices become overwhelming.
• Keeping a diary of what the voices say, to recognize patterns.
• Setting boundaries with the voices, such as: “I will not obey commands that harm myself or others.”
• Using grounding techniques—e.g., naming 5 real things you can see in the room, 4 you can touch, etc.

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8. Notes — Key Points & Clarifications for General Readers

• Hallucinations ≠ “insanity.”
• They are brain–mind symptoms with many possible causes.
• They do not automatically mean that a person is “irrational” or “dangerous.”

• Ordinary people can have experiences similar to hallucinations.
• Hypnagogic/hypnopompic hallucinations around sleep.
• Hearing one’s name called when nobody called—transient phenomena found in many healthy individuals.
• What matters is frequency, severity, interference with life, and the context of co-occurring disorders.

• Hallucinations and spiritual/supernatural beliefs
• In some cultures, “hearing voices” or “seeing something” is interpreted as religious/spiritual experience.
• Clinicians assess context: if the experience is not distressing, does not impair functioning, and aligns with cultural beliefs, it may not be considered a disorder.
• But if there is distress, impairment, or risky commands, mental health services should be involved.

• Treatment is not just “using drugs to suppress voices.”
• It is a long-term process combining medication, therapy, and social support.
• The goal is not only “voices gone,” but also improved quality of life, functioning, and relationships.

• Do not stop medication suddenly.
• Abruptly stopping antipsychotics → symptom relapse and risk of psychotic relapse.
• All changes should be made in collaboration with a clinician.

• Command hallucinations urging self-harm or violence = emergency.
• Immediate contact with a doctor, hospital, or mental health crisis line in the area is necessary.
• Early treatment reduces risk and long-term consequences.

Read Schizophrenia

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📚 References (Academic + Clinical + Neuroscience)

Organized by category so you can place them neatly at the end of an article and look professional.

1) Textbooks & Clinical Standards

• American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Text Revision (DSM-5-TR). 2022.
• World Health Organization. International Classification of Diseases 11th Revision (ICD-11): Mental, Behavioural and Neurodevelopmental Disorders.
• Sadock BJ, Sadock VA, Ruiz P. Kaplan & Sadock’s Comprehensive Textbook of Psychiatry.
• Stahl SM. Stahl’s Essential Psychopharmacology. Cambridge University Press.

2) Hallucinations — Core Research & Meta-analyses

• Waters F, Fernyhough C. “Auditory Hallucinations: Does a Continuum of Severity Exist? A Review of Cognitive Models.” Schizophrenia Bulletin.
• Hugdahl K. “Auditory Hallucinations as Aberrant Inner Speech.” World Journal of Psychiatry.
• Allen P et al. “The Neurobiology of Auditory Hallucinations.” Schizophrenia Bulletin.
• Jardri R, et al. “The Neurodynamic Organization of Modality-Specific Hallucinations.” Cerebral Cortex.
• Moseley P, Fernyhough C. “Self-Monitoring, Inner Speech and Auditory Verbal Hallucinations.” Schizophrenia Research.

3) Predictive Coding & Aberrant Salience Framework

• Friston K. “The Free-Energy Principle: A Unified Brain Theory?” Nature Reviews Neuroscience.
• Fletcher PC, Frith CD. “Perceiving is Believing: A Bayesian Approach to Explaining the Positive Symptoms of Schizophrenia.” Nature Reviews Neuroscience.
• Kapur S. “Psychosis as a State of Aberrant Salience: A Framework Linking Biology, Phenomenology, and Pharmacology in Schizophrenia.” American Journal of Psychiatry.

4) Glutamate–GABA Imbalance & NMDA Hypofunction

• Moghaddam B, Javitt D. “The Glutamate Hypothesis of Schizophrenia.” Annual Review of Psychiatry.
• Javitt DC. “Glutamate and Schizophrenia: Phencyclidine, NMDA Receptors, and Dopamine-Glutamate Interactions.” International Review of Neurobiology.
• Lewis DA. “Inhibitory Interneurons in Schizophrenia.” Nature Neuroscience.

5) Hallucinations Across Medical & Neurological Conditions

• Factor SA. “Hallucinations and Illusions in Parkinson’s Disease.” Movement Disorders.
• McKeith IG et al. “Consensus Guidelines for the Clinical Diagnosis of Lewy Body Dementia.” Neurology.
• Devinsky O, et al. “Epilepsy and Hallucinations: Temporal Lobe Pathways.” Epilepsy & Behavior.
• Maldonado JR. “Delirium Pathophysiology and Hallucinations.” Critical Care Clinics.
• Menon V. “Large-scale Brain Networks and Psychopathology.” Trends in Cognitive Sciences.

6) Trauma, Stress, and Hallucinations

• McCarthy-Jones S. Hearing Voices: The Histories, Causes and Meanings of Auditory Verbal Hallucinations.
• Read J, et al. “Childhood Trauma, Psychosis and Hallucinations: A Meta-analytic Review.” Acta Psychiatrica Scandinavica.
• van Os J, et al. “The Environment and Psychosis: Seasonality, Social Isolation, Urbanicity.” British Journal of Psychiatry.

7) Substance-Induced Hallucinations

• Bramness JG, et al. “Amphetamine-induced Psychosis.” Current Psychiatry Reports.
• Hasler F, et al. “LSD and Serotonin 5-HT2A Receptor Activation.” Biological Psychiatry.
• Lüscher C. “The Neurobiology of Addiction and Hallucinogens.” Nature Neuroscience.

Hallucinations • Auditory Hallucinations • Visual Hallucinations • Tactile Hallucinations • Olfactory Hallucinations • Gustatory Hallucinations • Psychosis • Positive Symptoms • Schizophrenia • Schizoaffective Disorder • Bipolar Psychosis • Major Depression with Psychotic Features • Delirium • Dementia • Lewy Body Dementia • Parkinson’s Psychosis • Substance-Induced Psychosis • Meth Psychosis • LSD Hallucinations • Dopamine Dysregulation • Aberrant Salience • Predictive Coding • Free-Energy Principle • Inner Speech Model • Self-Monitoring Deficit • Glutamate Hypofunction • NMDA Receptor • GABA Inhibition • Sensory Gating • Default Mode Network • Auditory Cortex • Temporal Lobe • Thalamus Dysfunction • Trauma and Psychosis • Childhood Trauma • Stress-Induced Hallucinations • Sleep Deprivation • Sensory Deprivation • Reality Testing • CBT for Psychosis • Antipsychotic Treatment • Neural Circuits of Perception • Brain Networks • Neuroscience of Hallucinations