A 32-year-old farmer is brought to the emergency department by his wife. The patient was reportedly anxious, sweaty, and complaining of a headache and chest tightness before losing consciousness on route to the hospital. Which of the following is mechanistically responsible for this patient's symptoms?

Irreversible inhibition of acetylcholinesterase

Reversible inhibition of acetylcholinesterase

Competitive inhibition of acetylcholine at post-junctional effector sites

Binding of acetylcholine agonists to post-junctional receptors

Inhibition of presynaptic exocytosis of acetylcholine vesicles

A 32-year-old man comes to the physician because of a 2 month history of difficulty sleeping and worsening fatigue. During this time, he has also had difficulty concentrating and remembering tasks at work as well as diminished interest in his hobbies. He has no suicidal or homicidal ideation. He does not have auditory or visual hallucinations. Vital signs are normal. Physical examination shows no abnormalities. Mental status examination shows a depressed mood and flat affect with slowed thinking and speech. The physician prescribes sertraline. Three weeks later, the patient comes to the physician again with only minor improvements in his symptoms. Which of the following is the most appropriate next step in management?

Continue sertraline for 3 more weeks

Augment with aripiprazole and continue sertraline

Provide electroconvulsive therapy

Change medication to duloxetine

Augment with phenelzine and continue sertraline

A 36-year-old woman complains of difficulty falling asleep over the past 4 months. On detailed history taking, she says that she drinks her last cup of tea at 8:30 p.m. before retiring at 10:30 p.m. She then watches the time on her cell phone on and off for an hour before falling asleep. In the morning, she is tired and makes mistakes at work. Her husband has not noticed excessive snoring or abnormal breathing during sleep. Medical history is unremarkable. She has smoked 5–7 cigarettes daily for 7 years and denies excess alcohol consumption. Her physical examination is normal. Which of the following is the best initial step in the management of this patient’s condition?

Continuous positive airway pressure

Panic disorder for USMLE Step 1: High-Yield Psychiatry Lessons

Diagnosis & Criteria - Defining the Dread

Hallmark: Recurrent, unexpected panic attacks.
Followed by ≥1 month of one or both:
- Persistent concern about future attacks or their consequences (e.g., "going crazy").
- Significant maladaptive behavior change related to attacks (e.g., avoiding exercise).
Panic Attack: Abrupt fear surge peaking within minutes with ≥4 of 13 official symptoms.
📌 Common symptoms: Palpitations, sweating, trembling, shortness of breath, chest pain, dizziness, paresthesias, derealization, fear of dying or losing control.

⭐ Key differentiator: The panic attacks are uncued ("out of the blue"). If attacks are consistently triggered by a specific situation, consider another diagnosis like a specific phobia or social anxiety disorder.

Pathophysiology - Brain on Fire

Neurotransmitter Dysregulation: Imbalance in key systems.
- Norepinephrine (NE): ↑ activity, especially from the locus coeruleus (the brain's "panic button").
- Serotonin (5-HT): ↓ levels, leading to poor mood and anxiety regulation.
- GABA: ↓ inhibitory function, causing unchecked neuronal firing.
Fear Circuitry: Hyperactive amygdala (fear center) with poor top-down control from the prefrontal cortex (PFC).

Chronic Stress, Brain Regions, and Anxiety Disorders

⭐ Patients with panic disorder often exhibit hypersensitivity to carbon dioxide ($CO_2$) inhalation, which can trigger panic attacks in a laboratory setting.

Clinical Features & Differentials - The Sudden Storm

Abrupt surge of intense fear peaking within minutes. Requires ≥4 of 13 DSM-5 symptoms:
- Palpitations, sweating, trembling, shortness of breath (SOB).
- Chest pain, dizziness, nausea, paresthesias.
- Derealization/depersonalization, fear of losing control or dying.
Crucial Differentials (Rule Out First):
- Medical: Myocardial infarction, pulmonary embolism, hyperthyroidism, pheochromocytoma, hypoglycemia.
- Substance-Induced: Caffeine, stimulants (cocaine, amphetamines), alcohol/sedative withdrawal.

⭐ Panic disorder patients often present to the ED fearing a heart attack; an EKG is essential to rule out cardiac ischemia.

Management - Taming the Terror

Long-Term (First-Line): SSRIs/SNRIs and CBT are cornerstones. SSRIs require 4-6 weeks for full effect. CBT focuses on exposure and cognitive restructuring.
Acute Management: Benzodiazepines provide rapid relief but should be used short-term (<4 weeks) as a bridge due to dependence risk.
Treatment Duration: Continue successful pharmacotherapy for at least 6-12 months after remission to prevent relapse.

⭐ Initial SSRI treatment can paradoxically worsen anxiety. Counsel patients on this risk and use a "start low, go slow" titration strategy.

Comorbidities & Prognosis - The Ripple Effect

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High‑Yield Points - ⚡ Biggest Takeaways

Recurrent, unexpected panic attacks followed by ≥1 month of persistent worry about future attacks or maladaptive behavior changes.

Strongly associated with agoraphobia, the fear of situations where escape might be difficult.

First-line treatment is a combination of SSRIs (e.g., sertraline) and Cognitive Behavioral Therapy (CBT).

Benzodiazepines are effective for acute management but are not preferred for long-term use due to dependence risk.

Always rule out underlying medical causes like hyperthyroidism, pheochromocytoma, and cardiac arrhythmias.

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Panic disorder