Hallucinogen-related disorders US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Hallucinogen-related disorders. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Hallucinogen-related disorders US Medical PG Question 1: A 21-year-old male college student is brought to the emergency department by the campus police after he was found yelling at a bookshelf in the library. His roommate does not know of any prior episodes similar to this. His vital signs are within normal limits. The patient appears unkempt. On mental status examination, he talks very fast with occasional abrupt interruptions. He is agitated. He is disoriented to time and repeatedly tells the physician, “I hear the sun telling me that I was chosen to save the universe.” Urine toxicology screen is negative. Which of the following is the most appropriate pharmacotherapy?
- A. Alprazolam
- B. Valproic acid
- C. Dexmedetomidine
- D. Haloperidol (Correct Answer)
- E. Ziprasidone
Hallucinogen-related disorders Explanation: ***Haloperidol***
- This patient presents with acute **psychosis** characterized by **auditory hallucinations**, **disorganized speech**, and **agitation**, making an **antipsychotic** the most appropriate initial treatment.
- **Haloperidol** is a potent **first-generation antipsychotic** effective for rapid tranquilization in acute psychotic episodes due to its fast onset of action and available parenteral formulation.
- It remains a widely used option for acute agitation with psychosis, particularly when rapid control is needed.
*Alprazolam*
- **Alprazolam** is a **benzodiazepine** primarily used for anxiety and panic disorders, acting as a CNS depressant.
- While it can reduce agitation, it does not directly address the underlying psychotic symptoms (hallucinations, delusions) and could exacerbate disorientation in a psychotic patient.
*Valproic acid*
- **Valproic acid** is a **mood stabilizer** and anticonvulsant, primarily used for bipolar disorder and epilepsy.
- It is not an appropriate first-line treatment for acute psychosis or agitation when the primary issue is psychotic symptoms, as its onset of action is slower for acute behavioral control.
*Dexmedetomidine*
- **Dexmedetomidine** is an alpha-2 adrenergic agonist used for sedation, particularly in ICU settings, that provides sedation without significant respiratory depression.
- While it could sedate this agitated patient, it does not treat the underlying psychosis and is generally not the first choice for agitation in acute psychiatric emergencies due to its primary action as a sedative rather than an antipsychotic.
*Ziprasidone*
- **Ziprasidone** is a **second-generation antipsychotic** that effectively treats psychosis and is available in both oral and IM formulations.
- While ziprasidone IM has rapid onset and is commonly used for acute agitation with psychosis, **haloperidol** has longer historical use and more extensive clinical experience in emergency settings for rapid tranquilization, though both are appropriate choices.
- Ziprasidone may cause QT prolongation, requiring ECG monitoring in some patients.
Hallucinogen-related disorders US Medical PG Question 2: A 23-year-old man is brought to the emergency department by the police for impaired cognition and agitation after being struck in the head at a local nightclub. The patient refuses to respond to questions and continues to be markedly agitated. An alcoholic smell is noted. His temperature is 36.9°C (98.4°F), pulse is 104/min, respirations are 24/min, and blood pressure is 148/95 mm Hg. He is confused and oriented only to person. Neurological examination shows miosis and nystagmus but is quickly aborted after the patient tries to attack several members of the care team. CT scan of the head shows no abnormalities. Ingestion of which of the following substances most likely explains this patient's symptoms?
- A. Lysergic acid diethylamide
- B. Phencyclidine (Correct Answer)
- C. Alcohol
- D. Heroin
- E. Methamphetamine
Hallucinogen-related disorders Explanation: ***Phencyclidine***
- **Phencyclidine (PCP)** intoxication is characterized by a combination of severe **agitation**, **aggression**, impaired cognition, nystagmus (vertical or horizontal), and miotic pupils, which precisely matches the patient's presentation.
- The patient's violent behavior and refusal to cooperate with examination despite an initial head injury also align with the dissociative and stimulant effects of PCP.
*Lysergic acid diethylamide*
- **LSD** typically causes hallucinations, altered perceptions, and dilated pupils (**mydriasis**), rather than the miotic pupils and marked aggression seen in this patient.
- While agitation can occur with LSD, the extreme violence and neurological signs like nystagmus point away from it as the primary cause.
*Alcohol*
- While alcohol can cause impaired cognition and agitation, the presence of **miosis** and **nystagmus** in this agitated state, especially given the degree of disorientation and aggression, is more characteristic of other substances.
- The "alcoholic smell" could be a red herring or co-ingestion, but the overall clinical picture is not solely attributable to acute alcohol intoxication.
*Heroin*
- **Heroin (opioid)** overdose typically causes **sedation**, respiratory depression, and pinpoint pupils (**miosis**), which is contrary to the agitation, aggression, and elevated vital signs described.
- The patient's high blood pressure and pulse are inconsistent with opioid effects.
*Methamphetamine*
- **Methamphetamine** intoxication leads to agitation, paranoia, and elevated vital signs (tachycardia, hypertension), but typically causes **mydriasis (dilated pupils)**, not miosis.
- Although agitation and aggression are significant features, the pupillary findings help differentiate it from PCP.
Hallucinogen-related disorders US Medical PG Question 3: A 19-year-old man is brought to the emergency department by his mother because of increasing agitation and aggression at home. He has a history of bipolar disorder. During the last week, he has refused to take his lithium medication because it makes him “feel empty inside.” The mother thinks he has experimented with illicit drugs in the past. He appears acutely agitated, yells at multiple medical staff members, and demands to be discharged. His temperature is 37.7°C (99.8°F), pulse is 95/min, respirations are 18/min, and blood pressure is 140/75 mm Hg. Haloperidol is administered and the patient is admitted. The next morning, the patient reports worsening neck pain. He states that his neck is locked to the left and he cannot move it. Examination shows rigidity of his upper body and neck, with the neck fixed in flexion and rotated to the left. Administration of which of the following is the most appropriate next step in the management of this patient?
- A. Bromocriptine
- B. Physostigmine
- C. Botulinum toxin
- D. Benztropine (Correct Answer)
- E. Diazepam
Hallucinogen-related disorders Explanation: ***Benztropine***
- The patient is experiencing an acute **dystonic reaction** due to haloperidol, presenting with severe neck rigidity, flexion, and rotation (torticollis).
- **Benztropine**, an anticholinergic medication, is the first-line treatment for acute dystonia as it blocks muscarinic receptors and restores the **acetylcholine-dopamine balance**.
*Bromocriptine*
- This is a **dopamine agonist** typically used to treat **neuroleptic malignant syndrome (NMS)**, which presents with fever, severe muscle rigidity, autonomic instability, and altered mental status.
- The patient's symptoms are more consistent with acute dystonia, not NMS, and his temperature is only mildly elevated.
*Physostigmine*
- This is an **acetylcholinesterase inhibitor** used to reverse anticholinergic toxicity, which would present with symptoms like dry mouth, blurred vision, delirium, and urinary retention.
- The patient's symptoms of acute dystonia are caused by **dopamine blockade** leading to a **relative excess of cholinergic activity**, not anticholinergic poisoning.
*Botulinum toxin*
- While effective for chronic dystonia and muscle spasms, **botulinum toxin** is not the appropriate first-line treatment for an acute drug-induced dystonic reaction.
- Its effects are not immediate, and it is usually reserved for cases refractory to oral medications or for focal dystonias.
*Diazepam*
- As a **benzodiazepine**, diazepam can provide some muscle relaxation and reduce anxiety, but it is not the primary treatment for reversing the neurochemical imbalance causing acute dystonia.
- It could be used as an adjunct for agitation or muscle spasms, but an anticholinergic is directly indicated for dystonia.
Hallucinogen-related disorders US Medical PG Question 4: A 34-year-old man presents to the behavioral health clinic for an evaluation after seeing animal-shaped clouds in the form of dogs, cats, and monkeys. The patient says that these symptoms have been present for more than 2 weeks. Past medical history is significant for simple partial seizures for which he takes valproate, but he has not had his medication adjusted in several years. His vital signs include: blood pressure of 124/76 mm Hg, heart rate of 98/min, respiratory rate of 12/min, and temperature of 37.1°C (98.8°F). On physical examination, the patient is alert and oriented to person, time, and place. Affect is not constricted or flat. Speech is of rapid rate and high volume. Pupils are equal and reactive bilaterally. The results of a urine drug screen are as follows:
Alcohol positive
Amphetamine negative
Benzodiazepine negative
Cocaine positive
GHB negative
Ketamine negative
LSD negative
Marijuana negative
Opioids negative
PCP negative
Which of the following is the most likely diagnosis in this patient?
- A. Delusion
- B. Alcohol withdrawal
- C. Visual hallucination
- D. Cocaine intoxication
- E. Illusion (Correct Answer)
Hallucinogen-related disorders Explanation: ***Illusion***
- The patient is seeing **animal shapes in the clouds**, which is a misinterpretation of a real external stimulus. This is the definition of an **illusion**.
- Unlike hallucinations, illusions involve a distorted perception of an existing object, rather than perceiving something that is not present.
*Delusion*
- A **delusion** is a **fixed, false belief** that is not amenable to change in light of conflicting evidence, and it is not what is being described here.
- The patient is experiencing a perceptual distortion, not a false belief system.
*Alcohol withdrawal*
- While the patient tests positive for alcohol, the symptoms described are **perceptual distortions** (misinterpretation of clouds), not typical signs of alcohol withdrawal which include tremors, seizures, and delirium tremens.
- The timeline of "more than 2 weeks" also makes acute alcohol withdrawal less likely, as withdrawal symptoms typically peak within days.
*Visual hallucination*
- A **hallucination** is a perception in the absence of an external stimulus; the patient would be seeing animals when no clouds (or other visual stimuli) are present.
- The patient is seeing animal shapes *in the clouds*, indicating an existing external stimulus that is being misinterpreted.
*Cocaine intoxication*
- While cocaine intoxication can cause psychiatric symptoms like paranoia and hallucinations, the specific description of **seeing animal shapes in clouds** (misinterpretation of a real stimulus) points more directly to an illusion rather than a primary effect of cocaine use.
- The patient's presentation does not include other common symptoms of acute cocaine intoxication like severe agitation, dilated pupils, or hyperthermia beyond a rapid heart rate.
Hallucinogen-related disorders US Medical PG Question 5: A 19-year-old man is brought to the emergency department by the police. The officers indicate that he was acting violently and talking strangely. In the ED, he becomes increasingly more violent. On exam his vitals are: Temp 101.1 F, HR 119/min, BP 132/85 mmHg, and RR 18/min. Of note, he has vertical nystagmus on exam. What did this patient most likely ingest prior to presentation?
- A. Marijuana
- B. Dextromethorphan
- C. Ketamine
- D. Phencyclidine (Correct Answer)
- E. Mescaline
Hallucinogen-related disorders Explanation: ***Phencyclidine***
- **Phencyclidine (PCP)** intoxication is characterized by acute behavioral changes, violence, hyperthermia, tachycardia, and hypertension.
- **Vertical nystagmus** is a classic and highly suggestive sign of PCP intoxication, due to its effect on cerebellar and vestibular pathways.
*Marijuana*
- Marijuana typically causes euphoria, relaxation, altered perception of time, and conjunctival injection, not aggression or vertical nystagmus.
- While it can impair coordination, it rarely leads to the extreme violence and specific vital sign abnormalities seen here.
*Dextromethorphan*
- Dextromethorphan (DXM) abuse can cause dissociative effects, hallucinations, nystagmus (often horizontal), and tachycardia.
- However, the severe violence and classic vertical nystagmus exhibited in this case are more characteristic of PCP.
*Ketamine*
- Ketamine, a dissociative anesthetic, can cause hallucinations, agitation, and nystagmus, similar to PCP.
- While it shares some effects with PCP, **vertical nystagmus** is more specifically associated with PCP toxicity.
*Mescaline*
- Mescaline is a psychedelic hallucinogen that primarily causes visual hallucinations, altered thought processes, and euphoria.
- It does not typically produce the severe violent behavior, hyperthermia, or characteristic vertical nystagmus seen with PCP.
Hallucinogen-related disorders US Medical PG Question 6: A 23-year-old male is brought by police officers from a social gathering due to combative behavior and altered mental status. The police say that phencyclidine was found on the premises. The patient is alone, and acquiring an accurate history proves difficult. However, you do learn that the patient is having visual hallucinations. Vital signs show a blood pressure of 155/95 mmHg, pulse is 103/min, respirations is 20/min, oxygen saturation of 99%. Airway, breathing, and circulation are intact. The patient appears violent, and is trying to remove his clothes. Multiple hospital staff are needed to restrain the patient in bed. A finger-stick glucose show 93 mg/dL. The team is unable to place an IV, and thus intramuscular midazolam is administered to achieve sedation; however, he is still agitated. What is the mechanism of action of the best alternative sedative drug for this patient?
- A. Mu-opioid receptor partial agonist
- B. Competitive opioid receptor antagonist
- C. Alpha-2 and H1 receptor antagonist
- D. Increases duration of chloride channel opening of GABA-A receptors
- E. Antagonist of D2 receptors (Correct Answer)
Hallucinogen-related disorders Explanation: ***Antagonist of D2 receptors***
- The patient is likely suffering from **phencyclidine (PCP) intoxication**, characterized by **agitation**, **combative behavior**, **altered mental status**, **hypertension**, **tachycardia**, and **visual hallucinations**.
- **Haloperidol**, a potent **D2 dopamine receptor antagonist**, is often the preferred second-line treatment for agitation in PCP intoxication when benzodiazepines are insufficient, as it effectively reduces the psychotic and agitated state.
*Mu-opioid receptor partial agonist*
- This mechanism describes drugs like **buprenorphine**. While used for opioid addiction, it is not an appropriate sedative for acute PCP intoxication.
- Using an opioid agonist or partial agonist in a combative, agitated patient with unclear history could worsen respiratory depression or complicate the clinical picture.
*Competitive opioid receptor antagonist*
- This describes **naloxone**, used to reverse opioid overdose. It would not be helpful for PCP intoxication, as PCP acts via different receptor systems (NMDA antagonism, dopamine reuptake inhibition).
- Administering naloxone in this scenario would have no therapeutic benefit for the patient's agitation and psychosis.
*Alpha-2 and H1 receptor antagonist*
- This describes the mechanism of drugs like **mirtazapine** (primarily antidepressant) or **clonidine** (alpha-2 agonist, not antagonist, used for sedation/hypertension but less effective for acute psychotic agitation).
- While some antipsychotics have H1 antagonism, this specific combination is not the primary mechanism of the most effective conventional antipsychotics used for severe agitation.
*Increases duration of chloride channel opening of GABA-A receptors*
- This mechanism describes **barbiturates**. While some barbiturates can cause sedation, they are generally not preferred as first-line agents in this situation due to a higher risk of respiratory depression and a narrow therapeutic index compared to benzodiazepines or antipsychotics.
- The initial intramuscular midazolam (a benzodiazepine) works by increasing the *frequency* of chloride channel opening, not duration, making this option incorrect for the *best alternative*.
Hallucinogen-related disorders US Medical PG Question 7: A 19-year-old man presents to a psychiatrist for the management of substance abuse. He reports that he started using the substance 2 years ago and that he smokes it after sprinkling it on his cigarette. He describes that after smoking the substance, he feels excited and as if he does not belong to himself. He also reports that when he is in his room, he sees vivid colors on the walls after using the substance; if he listens to his favorite music, he clearly sees colors and shapes in front of his eyes. There is no history of alcohol or nicotine abuse. The psychiatrist goes through his medical records and notes that he had presented with acute substance intoxication 1 month prior. At that point, his clinical features included delusions, amnesia, generalized erythema of his skin, tachycardia, hypertension, dilated pupils, dysarthria, and ataxia. Which of the following signs is also most likely to have been present on physical examination while the man was intoxicated with the substance?
- A. Increased sensitivity to pain
- B. Excessive perspiration
- C. Hyporeflexia
- D. Generalized hypotonia
- E. Nystagmus (Correct Answer)
Hallucinogen-related disorders Explanation: ***Nystagmus***
- The patient's symptoms of **dissociation** ("feels as if he does not belong to himself"), **visual hallucinations** (seeing vivid colors and shapes), delusions, amnesia, tachycardia, hypertension, dilated pupils, dysarthria, and ataxia are highly characteristic of **phencyclidine (PCP) intoxication**.
- **Nystagmus**, particularly **horizontal and vertical nystagmus**, is a classic and frequently observed sign in PCP intoxication due to its effects on the **cerebellum** and vestibular system.
*Increased sensitivity to pain*
- PCP is known for its **analgesic** and **anesthetic** properties, leading to **decreased sensitivity to pain**, not increased.
- This effect contributes to the potential for self-injurious behavior during intoxication.
*Excessive perspiration*
- While other stimulants can cause diaphoresis, PCP intoxication more typically presents with **dry skin** or normal perspiration despite **hyperthermia** as it interferes with cholinergic thermoregulation.
- The described **generalized erythema** suggests **vasodilation**, but **dry skin** is more often associated with the anticholinergic effects that can accompany PCP.
*Hyporeflexia*
- PCP intoxication commonly causes **hyperreflexia** and **spasticity**, not hyporeflexia, due to its excitatory effects on the **central nervous system**.
- **Muscle rigidity** and **seizures** are also possible, further indicating CNS excitation.
*Generalized hypotonia*
- PCP typically leads to **increased muscle tone** and **rigidity**, not generalized hypotonia.
- The patient's presentation with **ataxia** and **dysarthria** suggests cerebellar involvement, but this usually manifests with motor incoordination rather than widespread flaccidity.
Hallucinogen-related disorders US Medical PG Question 8: A 77-year-old woman is brought to her primary care provider by her daughter with behavioral changes and an abnormally bad memory for the past few months. The patient’s daughter says she sometimes gets angry and aggressive while at other times she seems lost and stares at her surroundings. Her daughter also reports that she has seen her mother talking to empty chairs. The patient says she sleeps well during the night but still feels sleepy throughout the day. She has no problems getting dressed and maintaining her one bedroom apartment. Past medical history is significant for mild depression and mild osteoporosis. Current medications include escitalopram, alendronic acid, and a multivitamin. The patient is afebrile, and her vital signs are within normal limits. On physical examination, the patient is alert and oriented and sitting comfortably in her chair. A mild left-hand tremor is noted. Muscle strength is 5 out of 5 in the upper and lower extremities bilaterally, but muscle tone is slightly increased. She can perform repetitive alternating movements albeit slowly. She walks with a narrow gait and has mild difficulty turning. Which of the following is the most likely diagnosis in this patient?
- A. Lewy body dementia (Correct Answer)
- B. Alzheimer's disease
- C. Serotonin syndrome
- D. Frontotemporal dementia
- E. Delirium
Hallucinogen-related disorders Explanation: ***Lewy body dementia***
- This patient exhibits **fluctuating cognition** (being lost and staring, behavioral changes), **recurrent visual hallucinations** (talking to empty chairs), and spontaneous motor features of **parkinsonism** (mild left-hand tremor, increased muscle tone, slow alternating movements, narrow gait, difficulty turning), all core features of Lewy body dementia.
- The **insidious onset** and progressive decline over months, along with the symptom triad, fit the diagnostic criteria for Lewy body dementia.
*Alzheimer's disease*
- While Alzheimer's involves memory loss and cognitive decline, it is not typically associated with **prominent early visual hallucinations** or **parkinsonian features** at presentation.
- Alzheimer's disease often presents with **memory impairment as the most prominent early symptom**, often preceding other cognitive deficits by years.
*Serotonin syndrome*
- This is an acute drug reaction characterized by a triad of **mental status changes**, **autonomic hyperactivity**, and **neuromuscular abnormalities**, usually developing rapidly after medication changes affecting serotonin levels.
- The patient's symptoms have been present for months, the vital signs are stable, and her medications (escitalopram) have been stable, making an **acute syndrome** like serotonin syndrome unlikely.
*Frontotemporal dementia*
- This type of dementia primarily affects personality, behavior, and language, with **prominent disinhibition or apathy**.
- While behavioral changes are present, the patient's prominent **visual hallucinations** and **parkinsonian features** are not characteristic of frontotemporal dementia.
*Delirium*
- Delirium is characterized by an **acute onset** and fluctuating course of attention and awareness, often triggered by an underlying medical condition, medication, or infection.
- The patient's symptoms have progressed over **several months**, rather than hours or days, and she is afebrile with stable vital signs, making delirium less likely.
Hallucinogen-related disorders US Medical PG Question 9: A 68-year-old man, accompanied by his wife, presents to his physician with cognitive decline and hallucinations. The patient’s wife tells that his cognitive impairment progressed gradually over the past 6 years, and first began with problems counting and attention. The hallucinations began approximately a year ago. The patient describes them as realistic and non-frightening; most often, he sees his cat accompanying him everywhere he goes. The patient’s wife also notes frequent episodes of staring spells in her husband and prolonged daytime napping. The blood pressure is 130/80 mm Hg with the orthostatic change to 110/60 mm Hg, heart rate is 75/min, respiratory rate is 13/min, and the temperature is 36.6°C (97.8°F). The patient is alert and responsive, but he is disoriented to time and place. He is pale and hypomimic. The cardiac, lung, and abdominal examinations are within normal limits for the patient’s age. The neurological examination is significant for a bilateral symmetrical cogwheel rigidity in the upper extremities. What would you most likely see on additional radiological investigations?
- A. Multiple lacunar infarcts on MRI
- B. Marked hippocampal atrophy on MRI
- C. Hypoperfusion and hypometabolism in frontal lobes on SPECT
- D. Decreased perfusion and dopaminergic activity in occipital lobes on PET (Correct Answer)
- E. Pontine 'hot-cross bun' sign on MRI
Hallucinogen-related disorders Explanation: ***Decreased perfusion and dopaminergic activity in occipital lobes on PET***
- This finding is characteristic of **dementia with Lewy bodies (DLB)**, which is strongly suggested by the patient's presentation with **cognitive fluctuations**, **visual hallucinations** (non-frightening, realistic), **parkinsonism** (cogwheel rigidity), and **REM sleep behavior disorder** (daytime napping/staring spells could be a manifestation). PET scans in DLB often show reduced occipital lobe uptake.
- The combination of **parkinsonism** (cogwheel rigidity) and **visual hallucinations** preceding or appearing early in the course of cognitive decline is a hallmark of DLB, which differentiates it from other dementias.
*Multiple lacunar infarcts on MRI*
- While lacunar infarcts can cause cognitive decline (**vascular dementia**), the clinical picture of prominent, well-formed visual hallucinations, parkinsonism, and cognitive fluctuations is less typical for purely vascular dementia.
- Vascular dementia usually presents with a step-wise decline in cognition and focal neurological deficits, which are not the primary features here.
*Marked hippocampal atrophy on MRI*
- **Hippocampal atrophy** is a hallmark of **Alzheimer's disease**, which typically presents with insidious memory loss as the primary symptom.
- The prominent early visual hallucinations and parkinsonism are not typical initial features of Alzheimer's disease.
*Hypoperfusion and hypometabolism in frontal lobes on SPECT*
- **Frontal lobe hypoperfusion/hypometabolism** on SPECT/PET is characteristic of **frontotemporal dementia (FTD)**.
- FTD typically presents with early behavioral changes or language deficits, not prominent visual hallucinations, parkinsonism, or significant cognitive fluctuations in the way seen in this patient.
*Pontine 'hot-cross bun' sign on MRI*
- The **'hot-cross bun' sign** on MRI is pathognomonic for **multiple system atrophy (MSA)**, specifically the **MSA-C subtype (cerebellar)**.
- While MSA can cause parkinsonism and autonomic dysfunction, it typically does not feature prominent visual hallucinations or significant cognitive decline as early and striking features as seen in this patient.
Hallucinogen-related disorders US Medical PG Question 10: Two days after undergoing hemicolectomy for colon cancer, a 78-year-old man is found agitated and confused in his room. He says that a burglar broke in. The patient points at one corner of the room and says “There he is, doctor!” Closer inspection reveals that the patient is pointing to his bathrobe, which is hanging on the wall. The patient has type 2 diabetes mellitus and arterial hypertension. Current medications include insulin and hydrochlorothiazide. His temperature is 36.9°C (98.4°F), pulse is 89/min, respirations are 15/min, and blood pressure is 145/98 mm Hg. Physical examination shows a nontender, nonerythematous midline abdominal wound. On mental status examination, the patient is agitated and oriented only to person. Which of the following best describes this patient's perception?
- A. Hallucination
- B. Illusion (Correct Answer)
- C. Loose association
- D. Delusion
- E. External attribution
Hallucinogen-related disorders Explanation: ***Illusion***
- An **illusion** is a **misinterpretation of an actual external stimulus**, as seen when the patient perceives his bathrobe as a burglar.
- This symptom, combined with **agitation**, **confusion**, and **recent surgery**, is highly suggestive of **delirium**.
*Hallucination*
- A **hallucination** is a **perception in the absence of an external stimulus**, meaning the patient would see or hear something that is not there at all.
- The patient here is clearly reacting to an existing object (the bathrobe), albeit misinterpreting it.
*Loose association*
- **Loose association** refers to a **thought disorder** where ideas shift from one subject to another in a way that is unrelated or minimally related, making the speech difficult to follow.
- This describes a pattern of thought, not a perceptual disturbance involving an external object.
*Delusion*
- A **delusion** is a **fixed, false belief** that is not amenable to change in light of conflicting evidence and is not in keeping with the individual's cultural background.
- While the patient believes a burglar is present, this belief arises from a direct misinterpretation of an object rather than a fixed, unfounded belief.
*External attribution*
- **External attribution** is a psychological concept where individuals ascribe responsibility for events or outcomes to **external factors** rather than internal ones.
- This term describes a cognitive bias in explaining causality, not a perceptual disturbance.
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