Learning Objectives
Master the clinical components of Psychosis. Distinguish between delusions, hallucinations, and disorganized thought, and recognize the high-yield diagnostic significance of different sensory modalities for the USMLE Step 1.
1. Core Components of Psychosis
Psychosis is a distorted perception of reality. It is a symptom, not a diagnosis, and can be seen in psychiatric, medical, or substance-induced conditions.
| Component | Clinical Definition & Details |
|---|---|
| Delusions | False, fixed, idiosyncratic beliefs that persist despite contrary evidence. Must be outside the patient’s culture/religion. |
| Disorganized Thought | Incoherent speech (“word salad”), tangentiality, or “loose associations” (derailment). |
| Hallucinations | Perceptions in the absence of external stimuli. Contrast with Illusions (misperceptions of real stimuli). |
Activity:
2. High-Yield Hallucination Types
The type of sensory modality involved often points toward a specific underlying etiology.
| Type | Common Association | Clinical Pearl |
|---|---|---|
| Auditory | Psychiatric illness | Classic for Schizophrenia. |
| Visual | Medical/Neurologic | Common in Delirium or drug intoxication. |
| Tactile | Withdrawal/Stimulants | “Cocaine crawlies” or alcohol withdrawal. |
| Olfactory | Temporal Lobe Epilepsy | Often an aura (e.g., burning rubber). |
| Hypnagogic | Going to sleep | Seen in Narcolepsy. |
| Hypnopompic | Waking up | “Pomped up in the morning.” |
Activity
High-Yield Clinical Pearls:
- Delusion vs. Idea: A delusion is fixed. If you present evidence and the patient does not waver, it is a Delusion.
- Illusion: Seeing a shadow and thinking it’s a cat = Illusion. Seeing a cat in an empty room = Hallucination.
- Tactile: If a patient feels “bugs crawling” under their skin, always screen for cocaine or alcohol withdrawal.
- Sleep Hallucinations: Use the mnemonic: Going to sleep = Hypnagogic; Pomped up to wake up = Hypnopompic.