Panic Disorder & Agoraphobia

Panic disorder is characterised by recurrent, unexpected panic attacks followed by at least a month of anticipatory anxiety or maladaptive behaviour change. Agoraphobia is the fear/avoidance of situations from which escape is difficult or help unavailable. Together they form one of the most heavily tested topics in NEET PG psychiatry, with favourite angles on the 13-symptom criteria, the locus ceruleus and CO₂-hypersensitivity theories, sodium lactate provocation, and the imipramine/SSRI treatment hierarchy.

Definitions & Classification

A panic attack is not a disorder by itself — it is a symptom that can occur in many conditions (specific phobia, social anxiety, PTSD, depression, medical illness). It is an abrupt surge of intense fear or discomfort that peaks within minutes (DSM-5 says "within minutes"; classically taught as within 10 minutes).

Panic attacks are described as:

• Unexpected (uncued): occur "out of the blue" with no obvious trigger — the hallmark of panic disorder.
• Situationally bound (cued): reliably provoked by exposure to a feared situation — typical of phobias.
• Situationally predisposed: more likely, but not invariably, on exposure.

Panic disorder requires recurrent unexpected attacks plus ≥1 month of either persistent worry about further attacks/their consequences or a significant maladaptive change in behaviour (e.g. avoidance).

High-yield: A single panic attack ≠ panic disorder. Recurrent unexpected attacks + ≥1 month anticipatory anxiety/behaviour change = panic disorder.

In DSM-5, agoraphobia was decoupled from panic disorder and is now a separate, independently codable diagnosis. ICD-10/ICD-11 traditionally classified "agoraphobia with/without panic disorder," but the modern trend (and the answer favoured in recent exams) is that agoraphobia and panic disorder are distinct entities that frequently co-occur.

Agoraphobia = marked fear/anxiety about ≥2 of 5 situations:

1. Using public transport
2. Being in open spaces (markets, car parks, bridges)
3. Being in enclosed spaces (shops, cinemas)
4. Standing in a queue or being in a crowd
5. Being outside the home alone

Duration for agoraphobia (and most DSM-5 phobic/anxiety disorders) is ≥6 months.

The 13 Symptoms of a Panic Attack

The DSM criterion requires ≥4 of 13 symptoms. This list is a perennial MCQ.

#	Symptom	Category
1	Palpitations / pounding heart / tachycardia	Cardiac
2	Sweating	Autonomic
3	Trembling or shaking	Motor
4	Shortness of breath / smothering	Respiratory
5	Feeling of choking	Respiratory
6	Chest pain or discomfort	Cardiac
7	Nausea / abdominal distress	GI
8	Dizziness, light-headedness, faintness	Neuro
9	Chills or heat sensations	Autonomic
10	Paraesthesias (numbness/tingling)	Neuro
11	Derealisation (unreality) / depersonalisation (detached from self)	Cognitive
12	Fear of losing control or "going crazy"	Cognitive
13	Fear of dying	Cognitive

High-yield: ≥4 of 13 symptoms peaking within ~10 minutes. A limited-symptom (paucisymptomatic) attack has <4 symptoms — still clinically relevant but does not meet full criteria.

Mnemonic — "STUDENTS FEAR the 3 C's": Sweating, Trembling, Unsteadiness/dizziness, Depersonalisation/derealisation, Excessive heart rate (palpitations), Nausea, Tingling (paraesthesia), Shortness of breath; FEAR = Fear of dying/losing control; 3 C's = Chest pain, Chills, Choking.

Epidemiology

• Lifetime prevalence of panic disorder ≈ 2–5% (commonly quoted ~2–3%).
• Female : Male ≈ 2–3 : 1.
• Bimodal age of onset: late adolescence (peak ~early-to-mid 20s) and a smaller peak in the mid-30s. Mean onset ~25 years.
• Strong association with mitral valve prolapse, asthma, migraine, IBS, and thyroid disease (associations, not causation — but tested).
• High comorbidity with major depression (up to ~50–65%), other anxiety disorders, and alcohol/substance use (self-medication).

Etiology & Pathophysiology

Panic disorder is the anxiety disorder with the strongest biological evidence, which is exactly why examiners love it.

Neuroanatomical model (Gorman's "fear network")

The amygdala is central, with projections to the:

• Locus ceruleus (noradrenaline) → autonomic/arousal symptoms,
• Periaqueductal grey → freezing/escape behaviour,
• Hypothalamus (HPA axis) → endocrine response,
• Parabrachial nucleus → respiratory symptoms.

Neurotransmitters

• Noradrenaline ↑ — hyperactive locus ceruleus (the principal noradrenergic nucleus, in the pons) is the classic "panic generator." Yohimbine (α₂ antagonist) ↑ NA and provokes panic; clonidine (α₂ agonist) suppresses it.
• Serotonin — dysregulation; basis of SSRI efficacy.
• GABA ↓ — reduced inhibitory tone; benzodiazepines act here. Flumazenil (BZD antagonist) can provoke attacks in patients.

High-yield: The locus ceruleus (noradrenergic, in the pons) is the most-tested anatomical substrate of panic.

Panic provocation ("panicogens") — favourite MCQ

Substances that reliably induce panic in patients but not controls:

Provoking agent	Mechanism
Sodium lactate (IV)	Classic Pitts & McClure test; metabolic/CO₂-related
CO₂ inhalation (5–35%)	Suffocation false-alarm / CO₂-hypersensitivity
Yohimbine	α₂ antagonist → ↑ noradrenaline
Caffeine	Adenosine antagonist
Flumazenil	BZD-receptor antagonist
Cholecystokinin (CCK-4)	Peptidergic
Isoproterenol	β-agonist

High-yield: Sodium lactate infusion is the classic experimental panic provocation test; Klein's suffocation false-alarm theory explains the exquisite CO₂ hypersensitivity seen in panic disorder.

Cognitive theory (Clark)

Patients catastrophically misinterpret benign bodily sensations (a normal palpitation → "I'm having a heart attack"), creating a vicious cycle: sensation → catastrophic thought → anxiety → more sensations. This underpins cognitive behavioural therapy (CBT).

Genetics

First-degree relatives have a 4–8× increased risk; twin studies show moderate heritability.

Clinical Features

• Sudden, crescendo anxiety peaking within minutes, lasting usually 20–30 minutes (rarely >1 hour).
• Prominent physical symptoms (cardiorespiratory dominate) → patients present repeatedly to A&E / cardiology, not psychiatry.
• Anticipatory anxiety: persistent dread of the next attack between episodes.
• Phobic avoidance: progressively restricting activities → secondary agoraphobia.
• May have nocturnal panic attacks (waking from sleep in panic) — distinguishes from night terrors/nightmares (no dream recall, occurs in non-REM).
• Demoralisation and secondary depression are common.

The natural course is typically chronic with a waxing-and-waning pattern.

Diagnosis & Investigation of Choice

Panic disorder is a clinical diagnosis — there is no confirmatory lab test. Investigations are done to exclude organic mimics, because the differential is broad and dangerous.

Stepwise approach:

Step 1 → Confirm recurrent unexpected attacks meeting ≥4/13 symptom criteria, peaking within minutes. Step 2 → Establish ≥1 month of anticipatory anxiety or behavioural change. Step 3 → Rule out organic causes (see below) and substance/medication effects (caffeine, cocaine, amphetamine, salbutamol, levothyroxine; or withdrawal from alcohol/benzodiazepines). Step 4 → Screen for comorbid depression, suicidality, and substance use.

Baseline organic workup: ECG, TSH (thyrotoxicosis), serum glucose, calcium, FBC/electrolytes; consider 24-hr urinary metanephrines/catecholamines if phaeochromocytoma suspected, and toxicology.

High-yield: There is no diagnostic investigation for panic disorder itself — tests exist only to exclude organic causes (do an ECG and TSH routinely).

Management

Treatment combines psychotherapy and pharmacotherapy; the gold standard is the combination.

Drug of choice

High-yield: SSRIs are the first-line / drug of choice for panic disorder. Imipramine (a TCA) is the classic / historically proven agent and remains a heavily examined answer.

Start low, go slow: panic patients are exquisitely sensitive to the early activation/jitteriness of SSRIs, which can transiently worsen panic. Begin at half the usual starting dose and titrate up. Onset of benefit ~2–4 weeks (full ~6–12 weeks).

Class	Examples	Role / Notes
SSRI	Paroxetine, sertraline, escitalopram, fluoxetine	First-line. Paroxetine & sertraline FDA-approved for panic
SNRI	Venlafaxine	First-line alternative
TCA	Imipramine, clomipramine	Classic effective agent; more side-effects, lethal in overdose
MAOI	Phenelzine	Effective but reserved (diet/interactions)
Benzodiazepine	Alprazolam, clonazepam	Fastest relief; for acute/bridging use only — dependence risk

Benzodiazepine caveat: alprazolam works within minutes and is excellent for acute attacks and as a bridge during the SSRI lag, but its short half-life, rebound anxiety, and dependence potential make it unsuitable for long-term monotherapy. Clonazepam (longer half-life) is preferred when a BZD is needed.

High-yield: β-blockers (propranolol) are NOT effective for panic disorder — they blunt peripheral symptoms only. They are used for performance/social anxiety, not panic. A common exam trap.

Psychotherapy

• Cognitive Behavioural Therapy (CBT) is the psychotherapy of choice and is first-line, equal in long-term efficacy to medication.
• Key CBT components: psychoeducation, cognitive restructuring of catastrophic misinterpretations, interoceptive exposure (deliberately inducing feared sensations e.g. hyperventilation, spinning), and breathing retraining.
• For agoraphobia: graded (systematic) in-vivo exposure to feared situations is the single most effective intervention.

Treatment duration

Continue pharmacotherapy for ≥12 months (often 1–2 years) after remission, then taper slowly to reduce relapse.

Complications

• Secondary agoraphobia and progressive functional disability/housebound state.
• Major depressive disorder and elevated suicide risk (panic disorder independently raises suicide attempts).
• Substance/alcohol use disorder from self-medication; benzodiazepine dependence from prescribed treatment.
• Repeated unnecessary cardiac investigations and ED visits.
• Demoralisation, occupational impairment, relationship strain.

Key Differentials

A panic attack is the great mimic. The differential separates into psychiatric and organic.

Condition	Discriminating clue
Specific / social phobia	Attacks are cued by a specific stimulus, never spontaneous
GAD	Continuous "free-floating" worry, not discrete crescendo attacks
PTSD	Attacks triggered by trauma reminders; re-experiencing, hypervigilance
Hyperthyroidism	Weight loss, heat intolerance, ↓TSH, persistent tachycardia
Phaeochromocytoma	Episodic headache + sweating + palpitations, ↑BP, ↑metanephrines
Hypoglycaemia	Relieved by glucose; relation to fasting
Arrhythmia (SVT) / ACS	ECG changes, structural disease
Substance effects	Caffeine, cocaine, amphetamines; alcohol/BZD withdrawal
Vestibular disorder	Dizziness/vertigo dominate, positional

High-yield: Phaeochromocytoma is the must-exclude organic mimic — the classic triad is episodic headache, sweating, palpitations with paroxysmal hypertension.

Eponyms & Named Concepts

• Pitts & McClure — sodium lactate provocation of panic.
• Klein's suffocation false-alarm theory — CO₂ hypersensitivity; also Klein described the "pharmacological dissection" showing imipramine blocks panic but not anticipatory anxiety.
• Gorman's neuroanatomical fear network — amygdala-centred model.
• Clark's cognitive model — catastrophic misinterpretation of bodily sensations.
• Da Costa's syndrome ("soldier's heart"/neurocirculatory asthenia) — historical description overlapping with panic.

Recently asked / exam angle

• "Number of symptoms required for a panic attack?" → 4 (of 13). Time to peak → within 10 minutes/minutes.
• "Drug of choice in panic disorder?" → SSRI (first-line); imipramine if asked the classic/older agent.
• "Which drug is NOT useful?" → Propranolol/β-blockers.
• "Panic provocation test / panicogen?" → Sodium lactate (also CO₂, yohimbine, caffeine).
• "Anatomical site / 'panic centre'?" → Locus ceruleus (noradrenergic, pons).
• "Theory explaining CO₂ sensitivity?" → Klein's suffocation false-alarm theory.
• "Best psychotherapy?" → CBT; for agoraphobia → graded exposure.
• "Agoraphobia in DSM-5 needs fear of how many situations?" → ≥2 of 5; duration ≥6 months.
• "Quickest symptomatic relief in an acute attack?" → Benzodiazepine (alprazolam), short-term only.
• DSM-5 change: agoraphobia is now a separate diagnosis from panic disorder.

Rapid revision

1. Panic attack = abrupt fear peaking within ~10 minutes, ≥4 of 13 symptoms.
2. Panic disorder = recurrent unexpected attacks + ≥1 month anticipatory anxiety/behaviour change.
3. Limited-symptom attack = <4 symptoms.
4. F:M ≈ 2–3:1; lifetime prevalence ~2–3%; onset late teens–mid 20s (bimodal).
5. Locus ceruleus (noradrenaline) = key panic site; GABA ↓, serotonin dysregulated.
6. Panicogens: sodium lactate, CO₂, yohimbine, caffeine, flumazenil, CCK-4.
7. Klein's suffocation false-alarm theory = CO₂ hypersensitivity.
8. No diagnostic test; investigate to exclude — do ECG + TSH; exclude phaeochromocytoma.
9. DOC = SSRI (start low, go slow); imipramine is the classic TCA; alprazolam for acute relief only.
10. β-blockers do NOT treat panic (used for performance anxiety).
11. CBT = first-line psychotherapy; graded in-vivo exposure for agoraphobia.
12. Treat for ≥12 months; agoraphobia needs fear of ≥2/5 situations for ≥6 months and is a separate DSM-5 diagnosis.