Key Facts

Phobias are characterised by marked, disproportionate fear of a specific object or situation, leading to avoidance. Despite recognising the fear as excessive, patients are unable to control their anxiety response. Phobias are highly treatable with exposure-based psychological therapy.

Epidemiology

Specific phobias have a lifetime prevalence of 7-12% (most common mental health disorders). Agoraphobia affects approximately 1.7% of the population. Women are affected approximately twice as often as men. Onset is typically in childhood for specific phobias and adolescence/early adulthood for agoraphobia.

Aetiology

• Classical conditioning: Direct traumatic experience with the feared stimulus → learned fear association
• Observational learning: Witnessing others' fearful responses (vicarious conditioning)
• Information transmission: Being told about dangers (cognitive pathway)
• Prepared learning theory (Seligman): Evolutionary preparedness to develop fears of ancestral threats (snakes, heights, spiders) more readily
• Genetic: Heritability ~30-40%; blood-injection-injury phobia has the highest heritability (~60%)

Pathophysiology

• Amygdala hyperactivation: Excessive threat detection for phobic stimuli
• Deficient prefrontal regulation: Failed cognitive control over fear response
• Blood-injection-injury phobia: Unique biphasic response — initial sympathetic activation followed by parasympathetic (vagal) dominance → bradycardia and syncope
• Exposure therapy mechanism: Extinction learning — new inhibitory memory formed that competes with original fear association

Specific Phobia

• Marked fear disproportionate to actual danger
• Immediate anxiety response on encountering stimulus (or anticipation)
• Avoidance of feared stimulus or endured with intense distress
• Significant functional impairment or marked distress about having the phobia
• Persistent — typically ≥6 months

Agoraphobia

• Fear/anxiety about ≥2 of: Public transport, open spaces, enclosed spaces, standing in line/crowds, being outside the home alone
• Fear of not being able to escape or get help if panic-like symptoms develop
• Active avoidance → may become housebound in severe cases

Red Flags

• Housebound due to agoraphobia — urgent psychological therapy referral
• Blood-injection-injury phobia in healthcare worker — significant occupational impact
• Comorbid depression or substance misuse
• Phobia causing significant social or occupational dysfunction

Bedside

• Clinical interview: Identify specific phobia type, triggers, avoidance patterns, functional impact
• PHQ-9/GAD-7: Screen for comorbid depression and generalised anxiety
• Functional assessment: Impact on work, social life, daily activities

Bloods

• Generally not required unless differential diagnosis includes medical condition
• TFTs: If anxiety symptoms suggest thyroid dysfunction

Special Tests

• Behavioural avoidance test (BAT): Standardised approach to phobic stimulus to assess severity
• Subjective Units of Distress Scale (SUDS): Self-rated 0-100 during exposure hierarchy

Non-pharmacological (First-line — NICE CG159)

• CBT with graded exposure (systematic desensitisation):
  • Construct fear hierarchy (SUDS ratings)
  • Graded exposure: Start with least anxiety-provoking situation, progress gradually
  • In-vivo exposure is more effective than imaginal exposure
  • Typically 5-10 sessions
• Applied tension technique (Öst): Specific to blood-injection-injury phobia — tense large muscle groups to maintain BP during blood exposure
• Virtual reality exposure therapy: Emerging evidence — effective for fear of heights, flying, spiders

Pharmacological

• Generally not first-line for specific phobias — CBT is preferred
• SSRI (sertraline, paroxetine): May be used for agoraphobia, especially with comorbid panic
• Propranolol 10-40mg PRN: For performance anxiety or specific situational phobias (e.g., flying)
• Benzodiazepines: Short-term for specific situations (e.g., diazepam 2-5mg before dental procedure) — does not produce lasting improvement

Referral Criteria

• Phobia causing significant functional impairment — IAPT (Improving Access to Psychological Therapies)
• Severe agoraphobia — specialist anxiety service
• Comorbid conditions requiring complex management

• Specific phobias: Very treatable — CBT with exposure has 80-90% response rate in many studies
• Single-session exposure therapy can be effective for some specific phobias (Öst model)
• Agoraphobia: More chronic course; ~30-40% remit without treatment; CBT improves outcomes significantly
• Without treatment: Specific phobias tend to persist — only ~20% spontaneously remit in adulthood
• Blood-injection-injury phobia: Applied tension technique highly effective (>90% improvement)
• Comorbid depression worsens prognosis for all phobia subtypes

Specific Phobia Subtypes

Exposure Therapy Principles