Hallucinations
Composed By Muhammad Aqeel Khan
Date 21/9/2025
Hallucinations are powerful, and often distressing, experiences when a person perceives something that isn’t actually present. Whether seeing, hearing, smelling, tasting, or feeling things that have no external stimulus, these experiences can feel vivid and real. For many, they are symptoms of underlying conditions; for others, temporary events tied to sleep, stress, or substances. This article will define hallucinations, explore their types, examine the neurological and psychological mechanisms, discuss common causes, real‐life impacts, diagnosis, treatment options, and guidance for when to seek professional help.
What are Hallucinations?
Hallucinations are perceptions in the absence of a corresponding external stimulus. The brain produces sensory experiences—vision, sound, smell, touch, taste—that appear real but are generated internally. Unlike illusions, which misinterpret real stimuli, hallucinations are entirely “internally generated.”
They may be transient or chronic; benign or distressing; isolated or part of a broader disorder. Understanding their type and cause is essential for compassionate and effective responses.
Types of Hallucinations
Hallucinations can affect any of the five senses. Some people experience only one type; others may have multiple. Here are the main categories:
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Visual hallucinations
Seeing objects, people, lights, shapes, shadows, distortions, colors or movement that aren’t there. Example: seeing animals or faces when none are present. -
Auditory hallucinations
Hearing sounds without external source: voices (speaking or whispering), music, noises. This is one of the most common types, especially in psychiatric conditions. -
Olfactory hallucinations
Smelling odors that are not present. These can be pleasant or unpleasant. -
Gustatory hallucinations
Tasting something without actual input (food, bitterness, metallic taste, etc.). -
Tactile (or somatic) hallucinations
Feeling sensations on or under the skin: things crawling, insects, pressure, warmth, or internal bodily sensations.
These are sometimes categorized as “positive” symptoms in psychiatric nomenclature (i.e. addition of perceptual phenomena) though that term concerns diagnostic classification rather than valuation.
Neurological & Psychological Mechanisms
Hallucinations are not “made up” in a purely mystical sense—they arise from understandable disruptions of brain function, sensory input, prediction, attentional, and emotional systems. Below are key mechanisms supported by scientific studies.
A. Sensory cortex hyperactivity & spontaneous activation
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Research shows that in auditory hallucinations, parts of the auditory cortex are active even when no sound is present. The brain misattributes internally generated signals.
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Visual hallucinations similarly involve visual cortex areas, especially in conditions where sensory input is low (e.g., eye disease, Charles Bonnet syndrome). Loss of input may reduce inhibition, causing spontaneous activity.
B. Predictive coding / Bayesian inference
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The brain constantly predicts sensory input; mismatches (prediction errors) ideally get corrected. When these systems are disrupted (too much top-down influence, or abnormal prior expectations), the brain may generate perceptions (hallucinations) to fill in gaps.
C. Network dysfunction / attention & salience
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Regions such as the insula, hippocampus, putamen, sensory cortices, and the salience network are implicated in hallucinations. These areas help decide which sensory representations become conscious. Dysfunction in connectivity or control may lead to normally suppressed internal representations becoming conscious.
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Abnormal “neural timescales” (how long a region holds or integrates information) have been linked to more severe hallucinations. Lower-level sensory regions with prolonged integration and dysfunction in higher levels of inference are part of recent models.
D. Neurotransmitter imbalances
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Dopamine overactivity in certain brain pathways (especially in schizophrenia) is strongly associated with auditory hallucinations.
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Other neurotransmitters (serotonin, glutamate, GABA, acetylcholine) are also involved depending on the condition (e.g., in Parkinson’s disease, Alzheimer’s disease). Cleveland Clinic+1
E. Sleep deprivation, sensory deprivation, trauma
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Lack of sleep, prolonged isolation or low sensory input can provoke hallucinations. The brain may compensate for missing input.
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Traumatic experiences are known to increase risk, especially for auditory hallucinations (voices) as part of PTSD or trauma-related disorders. Psychological stress interacts with neural systems.
Common Causes & Conditions Associated with Hallucinations
Some of the main causes include:
| Category | Examples / Conditions | Typical Hallucination Types / Features |
|---|---|---|
| Psychiatric disorders | Schizophrenia, schizoaffective disorder; Bipolar disorder with psychotic features; Major depressive disorder with psychosis; PTSD | Auditory most common; voices; command voices; sometimes visual or other modalities; often associated with mood or delusional content. |
| Neurological disorders | Parkinson’s disease; Alzheimer’s disease; Lewy body dementia; epilepsy; brain tumors; Charles Bonnet syndrome | Visual hallucinations frequent in Parkinson’s and visual/ophthalmologic disease; tactile or olfactory in temporal lobe epilepsy; gustatory rarely; fluctuations in consciousness. JNNP+2Cleveland Clinic+2 |
| Substance use / intoxication / withdrawal | Hallucinogens (LSD, psilocybin), alcohol / drug intoxication, medication side-effects, withdrawal syndromes | Visual, auditory, tactile often; distortions, illusions; onset timed with substance; resolution with cessation. |
| Sleep deprivation / extreme stress | Prolonged waking, delirium, hypnagogic/hypnopompic hallucinations (in falling asleep or waking) | Mixed visual/auditory; temporary; insight often preserved (realizing experiences aren’t real). |
| Sensory deprivation / impairment | Poor vision or hearing, blindness (Charles Bonnet), isolation | Visual hallucinations when vision is impaired; auditory if hearing loss; sensory filling-in phenomena. |
Impact on Daily Life
Hallucinations can vary widely in how much they disrupt life: in some people they are mild, occasional, or non-distressing; in others, they are frequent, debilitating, or cause fear, confusion, or social withdrawal.
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Functional impairment: Difficulty concentrating, working, sleeping, socializing. Voices can interrupt tasks; visual hallucinations can make mobility or tasks hazardous.
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Emotional distress: Fear, shame, anxiety, depression often accompany hallucinations—especially if the content is negative or frightening.
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Risk of harm: Sometimes hallucinations lead to dangerous behavior (responding to voices commanding harmful acts), accidental injury (misperceiving hazards), or self-harm.
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Stigma and misunderstanding: Because hallucinations are often associated with “mental illness,” people may hide them or avoid seeking help, worsening outcomes.
Diagnostic Approaches
Diagnosis involves determining what is causing the hallucinations, the type, frequency, severity, distress level, and impact. Key diagnostic steps:
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Clinical interview & history
Asking about when hallucinations started, modalities, content, triggers, duration, insight (does person realize they are not real?), and associated symptoms (delusions, mood symptoms, cognition changes). -
Physical examination & laboratory tests
To rule out medical causes: infections, metabolic disturbances (e.g., liver/kidney dysfunction), neurodegenerative disease, medication side-effects, vitamin deficiencies. -
Neurological / neuroimaging studies
MRI, CT scans if structural issues suspected; EEG if seizures or epilepsy suspected. -
Psychiatric assessment
Evaluate for psychiatric disorders (schizophrenia, bipolar disorder, mood disorders, PTSD), substance use disorders, sleep disorders. -
Cognitive & sensory testing
Assessment of sensory loss (vision, hearing), cognitive impairment (memory, orientation), attention, whether deficits in reality testing or predictive perception are present. -
Psychometric scales & self-report tools
For example, scales to measure frequency, severity, distress of auditory verbal hallucinations; standardized assessments for risk, quality of life.
Treatment Options
Treatment depends on cause, severity, distress, and risk. It often combines medication, psychotherapy, lifestyle changes, and sometimes neuromodulation.
A. Medications
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Antipsychotics are standard for hallucinations in schizophrenia, schizoaffective disorders, bipolar with psychotic features. First-generation and second-generation antipsychotics reduce severity and frequency.
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Acetylcholinesterase inhibitors may help in neurodegenerative conditions (e.g., Alzheimer’s, Parkinson’s, Lewy body dementia) when hallucinations are part of psychosis or visual misperceptions. Cleveland Clinic
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Adjusting or discontinuing medications or substances that provoke hallucinations.
B. Psychological Therapies
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Cognitive Behavioral Therapy for psychosis (CBTp): Helping patients change the relationship with hallucinations, challenge beliefs about voices, reduce the distress.
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Trauma-informed therapy, especially if past trauma or PTSD is involved.
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Avatar therapy: Particularly for persistent auditory verbal hallucinations; creating digital representation of voices to allow dialogue and reduce their distressing power. ScienceDirect
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Psychosocial support: peer support groups, coping strategies (mindfulness, distraction, acceptance), social skills training.
C. Neuromodulation and Non-Pharmacological Treatments
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Transcranial Magnetic Stimulation (TMS): Low-frequency TMS to parts of the auditory cortex has evidence for reducing auditory hallucination severity, especially when medications are insufficient.
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Non-invasive brain stimulation in other modalities: Transcranial Direct Current Stimulation (tDCS) etc. Research is promising but often limited in duration/effect size.
D. Lifestyle, Supportive & Complementary Measures
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Optimizing sleep hygiene: Poor sleep is a strong trigger.
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Stress reduction: mindfulness, relaxation, establishing safe and predictable routines.
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Sensory aids if needed (hearing aids, better lighting, etc.), especially in sensory deprivation cases.
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Psychoeducation: helping individuals and their support network understand hallucinations, reduce fear and stigma.
Real-World Examples
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In schizophrenia, auditory hallucinations (“hearing voices”) are among the defining positive symptoms. People may experience voices commenting, commanding, or insulting. With antipsychotic medication plus CBTp, many see reduced frequency and distress.
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Parkinson’s disease patients may experience visual hallucinations, especially in later disease stages or with certain medications. For example, seeing people or animals that aren’t there, particularly in dim light. Treatment may involve adjusting medication, ensuring good vision, and sometimes cholinesterase inhibitors. Cleveland Clinic+1
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Alzheimer’s or dementia with Lewy bodies often produce visual hallucinations and sometimes auditory, especially at night. Diagnoses and treatment need to weigh cognitive decline and medication side effects.
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PTSD survivors may hear voices reflecting traumatic experiences. Therapy focusing on meaning, narrative therapy, trauma processing often helps.
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Sleep deprivation cases: people pulling all-nighters, or those in delirium (e.g. due to infection or metabolic disturbance) may have transient hallucinations which resolve with good care.
Limitations & Challenges in Treatment
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Medications often have side effects (weight gain, metabolic issues, sedation). Some hallucinations persist despite treatment.
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Psychological therapies may need specialized practitioners; access may be limited.
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Some modalities (like neuromodulation) have varying effectiveness, limited duration of effect, cost, and may not be suitable for all.
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Insight may be limited: some individuals believe experiences are real, which makes treatment engagement harder.
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Stigma, fear, and shame often lead people to conceal hallucinations, delaying diagnosis and support.
When to Seek Professional Help
If you or someone you care about is experiencing hallucinations, consider seeking professional help under these conditions:
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Hallucinations are frequent, persistent, or worsening.
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They cause distress, fear, anxiety, or interfere with daily functioning (work, relationships, sleep).
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Hallucinations command harmful behaviors, or you feel you might act on them.
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They occur along with mood changes (depression, mania), delusions, or confusion.
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There may be medical or neurological causes (e.g. head injury, seizures, fever, changes in medications).
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Insight is lost (you believe the hallucinations are definitely real and unchangeable).
Early treatment usually improves outcomes. A professional (psychiatrist, neurologist, or clinical psychologist) can do assessment, find causes, and tailor treatment you can live with.
Conclusion
Hallucinations are complex phenomena arising from interactions of brain sensory systems, prediction/feedback mechanisms, attention, emotional states, and sometimes pathology. They affect people in diverse ways — sometimes mildly, sometimes profoundly. The good news: science offers many insights into how they arise and how they can be managed. With a combination of medical care, psychological support, lifestyle adjustments, and compassionate understanding, many people find relief and ways to live meaningfully with or without their symptoms.
References
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Hare SM, et al. “Hallucinations: A Functional Network Model of How Sensory Representations Become Selected for Conscious Awareness in Schizophrenia.” Frontiers in Neuroscience, 2021.
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Sommer IE, et al. “The Treatment of Hallucinations in Schizophrenia.” PMC.
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Zmigrod L, et al. “The Neural Mechanisms of Hallucinations: A Meta-analysis.” ScienceDirect
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Cassidy CM, et al. “A Perceptual Inference Mechanism for Hallucinations.” Current Biology, 2018.
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O’Brien J, et al. “Visual hallucinations in neurological and ophthalmological disease.” Journal of Neurology, Neurosurgery & Psychiatry, 2020.
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Studies on psychological therapies: Thomas N, et al., 2014, “Psychological Therapies for Auditory Hallucinations (Voices)”; etc.