specific phobia

**Definition (DSM-5-TR):** Marked fear/anxiety about a specific object or situation that (1) is almost always provoked immediately on exposure, (2) is actively avoided or endured with intense fear, (3) is out of proportion to the actual danger and sociocultural context, (4) is persistent (typically ≥6 months), and (5) causes clinically significant distress or impairment. It is not better explained by another disorder (e.g., panic disorder, OCD, PTSD, social anxiety disorder, agoraphobia). In children, fear may be expressed as crying, tantrums, freezing, or clinging.

**Subtypes (DSM-5 specifiers):** - Animal (spiders, snakes, dogs, insects) – often begins in childhood - Natural environment (heights, storms, water) - Blood-injection-injury – unique **vasovagal response**: initial tachycardia/hypertension followed by bradycardia, hypotension, and **syncope**; strong familial component - Situational (flying, elevators, enclosed spaces/claustrophobia, driving) - Other (choking, vomiting, loud sounds, costumed characters)

**Epidemiology/Pathophysiology:** - Among the most common psychiatric disorders (lifetime prevalence ~10%); more common in women (except blood-injection-injury is more balanced). - Onset usually in childhood or adolescence. - Mechanisms: classical conditioning (traumatic experience), observational learning, informational transmission, and genetic predisposition. Avoidance is negatively reinforced, which maintains the phobia. - Neurobiology: hyperactivity of the **amygdala** (fear processing), insula, and anterior cingulate, with reduced prefrontal regulation.

**Clinical presentation:** Exposure → immediate anxiety/panic-like symptoms (tachycardia, sweating, tremor, dyspnea). Patients recognize the fear is excessive (adults), unlike delusional fear. Anticipatory anxiety is common.

**Differential (high-yield distinctions):** - *Social anxiety disorder:* fear of scrutiny/embarrassment in social or performance situations. - *Agoraphobia:* fear of ≥2 situations (public transit, open/enclosed spaces, crowds, being outside alone) because escape may be difficult or help unavailable. - *Panic disorder:* recurrent unexpected panic attacks with persistent worry about attacks. - *PTSD:* fear tied to a traumatic event with re-experiencing, hyperarousal, and avoidance. - *OCD:* avoidance driven by obsessions (e.g., contamination).

**Treatment:** - **First-line: CBT with exposure therapy** – systematic desensitization (graded exposure with relaxation), flooding (immediate full-intensity exposure), or in vivo/virtual reality exposure. Highly effective, often in a single session. - Blood-injection-injury: **applied tension** technique (tensing muscles to raise BP and prevent fainting). - Pharmacotherapy has limited role. Short-acting **benzodiazepines** or **β-blockers** (e.g., propranolol) may be used for infrequent, predictable exposure (e.g., a flight). SSRIs are not typically effective for isolated specific phobia. Avoid reliance on benzodiazepines because they can impair extinction learning.

**Board pearls:** - "Fear of a specific stimulus, avoidance, >6 months" → specific phobia; treat with exposure therapy. - Systematic desensitization = relaxation + graded hierarchy (counterconditioning; based on classical conditioning). - Flooding = prolonged exposure to the feared stimulus without escape. - Blood/needle phobia → syncope (vasovagal). - Performance-only anxiety (e.g., public speaking) → social anxiety disorder, performance only specifier; propranolol helpful.