A 26-year-old man is brought to the emergency department by his wife because of bizarre and agitated behavior for the last 6 weeks. He thinks that the NSA is spying on him and controlling his mind. His wife reports that the patient has become withdrawn and at times depressed for the past 3 months. He lost his job because he stopped going to work 4 weeks ago. Since then, he has been working on an invention that will block people from being able to control his mind. Physical and neurologic examinations show no abnormalities. On mental status examination, he is confused and suspicious with marked psychomotor agitation. His speech is disorganized and his affect is labile. Which of the following is the most likely diagnosis?

Schizotypal personality disorder

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 24-year-old woman is brought to the emergency department by her roommate because of bizarre behavior and incoherent talkativeness for the past week. Her roommate reports that the patient has been rearranging the furniture in her room at night and has ordered a variety of expensive clothes online. The patient says she feels “better than ever” and has a lot of energy. She had absence seizures as a child and remembers that valproate had to be discontinued because it damaged her liver. She has been otherwise healthy and is not taking any medication. She is sexually active with her boyfriend. She does not smoke, drink alcohol, or use illicit drugs. Physical and neurologic examinations show no abnormalities. Her pulse is 78/min, respirations are 13/min, and blood pressure is 122/60 mm Hg. Mental status examination shows pressured and disorganized speech, flight of ideas, lack of insight, and affective lability. Which of the following is the best initial step before deciding on a therapy for this patient's condition?

Obtain TSH, β-hCG, and serum creatinine concentration

Obtain CBC, liver function studies, and beta-HCG

Obtain BMI, HbA1c, lipid levels, and prolactin levels

Perform urine drug testing and begin cognitive behavior therapy

Assess for suicidal ideation and obtain echocardiography

A 42-year-old female presents to her primary care provider for an annual checkup. She reports feeling sad over the past few months for no apparent reason. She has lost interest in swimming, which she previously found enjoyable. Additionally, she has had trouble getting a full night’s sleep and has had trouble concentrating during the day. She has lost 15 pounds since her last visit one year prior. Which of the following sets of neurotransmitter levels is associated with this patient’s condition?

Decreased norepinephrine, decreased serotonin, decreased dopamine

Decreased acetylcholine, normal serotonin, normal dopamine

Decreased GABA, decreased acetylcholine, increased dopamine

Increased norepinephrine, decreased serotonin, decreased GABA

Increased acetylcholine, increased serotonin, decreased dopamine

Depression with psychotic features for USMLE Step 3: High-Yield Psychiatry Lessons

Diagnosis & Core Features - Spotting the Shadows

Foundation: Patient must meet full DSM-5 criteria for a Major Depressive Episode (MDE).
- ≥5 of 9 SIGECAPS symptoms for ≥2 consecutive weeks.
- Must include either depressed mood or anhedonia (loss of interest/pleasure).
Psychosis Overlay: Presence of delusions (fixed, false beliefs) and/or hallucinations (sensory perceptions without external stimuli).
- Mood-Congruent: Content aligns with depressive themes (e.g., guilt, disease, death, nihilism, deserved punishment).
- Mood-Incongruent: Content does not involve typical depressive themes.
Critical Timing: Psychotic symptoms occur exclusively during major depressive episodes.

⭐ If psychosis occurs for ≥2 weeks in the absence of a major mood episode, the diagnosis is more likely Schizoaffective Disorder.

Pathophysiology & Neurobiology - Brain Under Siege

HPA Axis Hyperactivity: ↑ Cortisol from chronic stress.
- Causes glucocorticoid receptor resistance, leading to hippocampal atrophy.
Dopamine (DA) Dysregulation:
- ↑ Mesolimbic DA → positive psychotic symptoms.
- ↓ Mesocortical DA → negative symptoms & cognitive deficits.
Monoamine & Glutamate Imbalance:
- ↓ Serotonin (5-HT) & Norepinephrine (NE) → depressed mood.
- ↑ Glutamate → excitotoxicity.
Neuroinflammation: ↑ Pro-inflammatory cytokines (e.g., IL-6, TNF-α).

⭐ Failure to suppress cortisol with dexamethasone is strongly associated with psychotic depression, indicating severe HPA axis dysfunction.

HPA axis and FKBP5 in psychotic depression

Clinical Workup & Differentials - Ruling Out Mimics

Initial Labs: Rule out organic causes with CBC, CMP, TSH, Vitamin B12/folate, and urine toxicology.
Neuroimaging (CT/MRI): Consider for late-onset psychosis or if neurological signs are present.
Primary Goal: Differentiate from other primary psychotic disorders based on symptom timing.

⭐ In psychotic depression, psychotic features resolve with the resolution of the mood episode. In contrast, schizoaffective disorder requires at least 2 weeks of psychosis without mood symptoms.

Treatment & Management - Restoring the Light

First-Line: Combination therapy is key. Monotherapy with an antidepressant is ineffective.
- Antidepressant (SSRI/SNRI) + Antipsychotic (SGA).
- Example: Sertraline + Olanzapine.
ECT (Electroconvulsive Therapy): Most effective & rapid treatment.
- Consider for severe suicidality, catatonia, malnutrition, or treatment resistance.

⭐ High-Yield: Antidepressant monotherapy can worsen psychosis in these patients and is considered malpractice.

Psychotic Depression Treatment Algorithm

High‑Yield Points - ⚡ Biggest Takeaways

A subtype of Major Depressive Disorder (MDD) where patients experience hallucinations or delusions.

Psychotic features are typically mood-congruent, involving themes of guilt, deserved punishment, or nihilism.

Differentiate from schizoaffective disorder: psychosis occurs only during depressive episodes.

First-line treatment is combination therapy with an antidepressant PLUS an antipsychotic.

Electroconvulsive therapy (ECT) is a highly effective primary treatment, especially for severe or urgent cases.

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