# PLAB 1 Psychiatry Questions: 10 Free Practice MCQs

> 10 free PLAB 1 psychiatry questions with answers and explanations, from a bank of 77 psychiatry questions. Try them now, no sign up.

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Last updated: 2026-10-29

Ten PLAB 1-style psychiatry questions with the answer and the reasoning behind it. They come from the UK.med bank, which has 77 psychiatry questions and many more across every topic.

1. 1 / 10  
In England, a 70-year-old with a urinary infection and mild dementia refuses cannulation. The doctor has not assessed whether acute confusion is affecting the patient’s ability to decide.  
What is the most accurate interpretation of the refusal?  
Show answer

**Answer: A.** It does not establish capacity or incapacity; assess the patient’s ability for this decision

**Why:** A refusal must be taken seriously but does not itself settle capacity. Assess the decision-specific test, including whether an impairment or disturbance causes inability to understand, retain, use or weigh relevant information, or communicate a decision.

  * **B.** Dementia alone cannot establish inability to make this decision.
  * **C.** Communicating a choice is only one part of the functional test; the patient must also understand, retain and use or weigh relevant information.
  * **D.** Refusal of physical treatment is not a basis for Mental Health Act detention.  
Sources: Mental Capacity Act 2005, sections 1 to 3
2. 2 / 10  
A 23-year-old woman is brought to the hospital by police. She has acute mania, is highly agitated, and has been walking in traffic because she believes she is immortal. She refuses admission to the psychiatric ward. She is not known to the local psychiatric services.  
Which section of the Mental Health Act 1983 is most appropriate to authorize her detention for assessment in hospital?  
Show answer

**Answer: C.** Section 2

**Why:** The Mental Health Act 1983 (amended 2007) governs compulsory admission. Section 2 allows detention for assessment for up to 28 days and cannot be renewed. Section 3 is for treatment and lasts up to 6 months (renewable). Both require two medical recommendations (one must be Section 12 approved) and an application by an AMHP. Section 4 is for 72-hour emergencies when Section 2 is impractical.

  * **A.** Section 3 is for admission for treatment for up to 6 months. It is used when the patient's diagnosis and treatment plan are already established, which is not the case for this first presentation.
  * **B.** Section 4 is an emergency admission section lasting up to 72 hours, requiring only 1 doctor. It should only be used when waiting for a second doctor for Section 2 would cause dangerous delay, which is not stated here.
  * **D.** Section 5(2) is a doctor's holding power used only for patients who are \*already\* voluntary inpatients in a hospital, not for patients presenting to ED or from the community.  
Sources: Mental Health Act 1983; GMC Good Medical Practice
3. 3 / 10  
A 17-year-old girl with severe anorexia nervosa (BMI 11.2) is admitted to a specialized inpatient unit. She is started on a structured refeeding programme. On day 3, she develops marked muscle weakness, confusion, and peripheral edema.  
Which of the following is the most likely biochemical abnormality causing her symptoms, and how should it be managed?  
Show answer

**Answer: B.** Severe hypophosphataemia (refeeding syndrome); treat by immediately replacing phosphate and thiamine, and restricting fluid/calories

**Why:** Refeeding syndrome is a metabolic complication that occurs when nutritional support is given to severely malnourished patients. The shift from fat to carbohydrate metabolism triggers insulin release, driving phosphate, potassium, and magnesium into cells, causing severe serum depletion. Hypophosphataemia leads to ATP depletion, causing muscle weakness, respiratory failure, arrhythmias, and death. Management requires slow refeeding (starting at 5-10 kcal/kg/day), thiamine supplementation, and prophylactic electrolyte replacement.

  * **A.** Refeed syndrome causes electrolyte depletion (hypophosphataemia, hypokalaemia, hypomagnesaemia), not hypercalcaemia.
  * **C.** Refeed syndrome causes fluid retention and sodium overload/dilutional hyponatremia due to insulin-mediated sodium reabsorption in the kidneys, not hypernatremic dehydration.
  * **D.** While hypoglycemia can occur in starvation, the combination of muscle weakness, confusion, and edema on day 3 of refeeding is diagnostic of refeeding syndrome. Giving concentrated dextrose without thiamine is highly dangerous.  
Sources: NICE CG32: Nutrition Support for Adults
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5. 4 / 10  
A 34-year-old man presents with a 2-year history of multiple, fluctuating physical symptoms including abdominal pain, headache, bloating, joint pain, and burning sensations. He has undergone numerous investigations and scans under various medical specialties, all of which are normal. He remains highly distressed and is convinced his symptoms are due to an undiagnosed physical disease, despite reassurance.  
What is the most likely diagnosis?  
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**Answer: C.** Somatisation disorder

**Why:** Somatisation disorder (classified under bodily distress disorder in newer systems) presents with multiple, variable physical symptoms affecting several organ systems, persisting for years, with a refusal to accept medical reassurance. Hypochondriacal disorder is defined by preoccupation with having a specific disease. In conversion disorder, symptoms are typically neurological and mimic organic deficits.

  * **A.** Hypochondriasis involves a preoccupation with having a \*specific\* serious disease (e.g. cancer, HIV), rather than a focus on multiple fluctuating symptoms.
  * **B.** Conversion disorder involves loss of motor or sensory function (e.g. pseudoseizures, paralysis, blindness) showing incompatibility with neurological disease.
  * **D.** Malingering involves conscious, intentional feigning of symptoms for external incentives (e.g. financial gain, avoiding work), which is not described here.  
Sources: ICD-10 / DSM-5 Classification of Somatoform Disorders
6. 5 / 10  
A 16-year-old female presenting with severe restrictive eating and a body mass index (BMI) of 14 kg/m² is observed to have fine, soft downy hair across her back and limbs.  
What is this sign called?  
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**Answer: C.** Lanugo

**Why:** Lanugo hair is fine downy body hair that develops as a physiological adaptation to starvation and body temperature loss in severe anorexia nervosa. Hirsutism refers to androgen-dependent male pattern hair growth, alopecia means hair loss, and Russell's sign refers to knuckle calluses caused by repeated self-induced vomiting.

  * **A.** Male pattern hair growth.
  * **B.** Hair loss.
  * **D.** Calluses on knuckles from vomiting.  
Sources: Oxford Handbook of Psychiatry
7. 6 / 10  
A 9-year-old has been persistently inattentive, impulsive and overactive since age 4\. Difficulties are reported both at home and school and impair learning. There is no neuropsychological test result in the referral.  
Which diagnosis should be assessed?  
Show answer

**Answer: D.** Attention deficit hyperactivity disorder The diagnosis is made clinically from symptoms, developmental history, impairment and evidence across settings.

**Why:** The history supports assessment for ADHD because symptoms began in childhood, occur in more than one setting and impair functioning. NICE does not require neuropsychological testing to establish the diagnosis.

  * **A.** A learning disorder may coexist, but it does not account for the pervasive hyperactivity and impulsivity described.
  * **B.** Autism assessment requires evidence of social communication differences and restricted or repetitive behaviours, which are not described.
  * **C.** Sleep problems can mimic or worsen inattention, but no sleep symptoms are reported and they would not explain the full history by themselves.  
Sources: NICE NG87
8. 7 / 10  
In England, a 74-year-old with mild dementia refuses antibiotics for a chest infection. The doctor has explained the options and concludes that the patient understands and weighs the information and communicates a consistent choice.  
What is the appropriate course of action?  
Show answer

**Answer: D.** Respect the informed refusal, discuss alternatives and document the decision

**Why:** The patient has capacity for this decision, so their informed refusal must be respected. Discuss acceptable alternatives and document the information given and the patient’s decision.

  * **A.** A capacitous adult may refuse treatment, even when clinicians consider the choice risky.
  * **B.** Family members cannot override a decision made by an adult who has capacity.
  * **C.** The Mental Health Act is not a route to treat a physical infection against a capacitous refusal.  
Sources: Mental Capacity Act 2005, sections 1 to 3; GMC, Decision making and consent
9. 8 / 10  
A 42-year-old man with bipolar affective disorder is admitted with nausea, vomiting, a coarse hand tremor, ataxia, slurred speech, and muscle weakness. His lithium level is checked and is 2.1 mmol/L (therapeutic range 0.4-1.0 mmol/L). His partner mentions he recently started taking a medication for lower back pain.  
Which of the following medications is most likely to have precipitated this patient's clinical presentation?  
Show answer

**Answer: A.** Naproxen

**Why:** Lithium is excreted almost entirely by the kidneys. Drugs that decrease renal clearance can precipitate lithium toxicity. The key culprits are NSAIDs (e.g. Naproxen, Ibuprofen), ACE inhibitors (e.g. Ramipril), and diuretics (especially thiazides like Bendroflumethiazide). Signs of toxicity appear when levels exceed 1.5 mmol/L and include coarse tremor, hyperreflexia, ataxia, confusion, and seizures.

  * **B.** Paracetamol does not affect renal function or lithium clearance and is safe to use concurrently.
  * **C.** Penicillin antibiotics do not significantly interact with lithium or impair its renal excretion.
  * **D.** Propranolol is a beta-blocker that can actually be used to treat lithium-induced fine tremor, and does not increase lithium levels.  
Sources: BNF Lithium Monograph; NICE CG185
10. 9 / 10  
A 25-year-old man is diagnosed with schizophrenia and is started on an antipsychotic medication. He reports an improvement in his symptoms, including a reduction in hallucinations and delusions.  
What is the primary mechanism of action of this medication?  
Show answer

**Answer: A.** Dopamine receptor antagonism

**Why:** Antipsychotic medications primarily work by blocking dopamine receptors in the brain, which is thought to be responsible for the development of psychotic symptoms. This is a key mechanism of action for these medications and is essential for their therapeutic effects.

  * **B.** While serotonin receptor agonism may contribute to the therapeutic effects of some medications, it is not the primary mechanism of action for antipsychotic medications.
  * **C.** GABA receptor agonism is not a primary mechanism of action for antipsychotic medications.
  * **D.** Norepinephrine receptor antagonism is not a primary mechanism of action for antipsychotic medications.  
Sources: NICE Guideline NG10
11. 10 / 10  
A 26-year-old man is brought to the emergency department by paramedics. He is unresponsive with a respiratory rate of 5 breaths/minute, pinpoint pupils, and cyanosis of his lips. Intravenous access is obtained.  
What is the most appropriate medication and administration strategy to reverse this presentation?  
Show answer

**Answer: C.** Intravenous Naloxone, titrated in small incremental doses to restore adequate respiration without inducing severe withdrawal

**Why:** Opioid toxicity is characterized by the triad of respiratory depression, pinpoint pupils, and coma. Naloxone is a competitive opioid antagonist. In patients who are not in cardiac arrest, Naloxone is administered in small, titrated IV doses (400 mcg is standard, but starting lower at 100-200 mcg is preferred in dependent users) to restore respiration while avoiding the precipitation of severe withdrawal syndromic agitation.

  * **A.** Giving a massive bolus of Naloxone causes acute withdrawal, severe pain, agitation, and potentially flash pulmonary edema, and is not recommended unless in cardiac arrest.
  * **B.** Flumazenil is the antidote for benzodiazepine overdose, not opioid overdose. Using it in chronic users can precipitate life-threatening seizures.
  * **D.** While airway support is vital, pharmacological reversal with Naloxone is highly effective and avoids the need for invasive ventilation in most cases.  
Sources: BNF Naloxone Monograph; Resuscitation Council UK guidelines

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